Time to pay it forward ... thanks to all those whose posts helped me get the job done right.
A brand new 2013 Ridgeline RTL should have a better sound system than a 160 watt 6-disc CD change ... and since I had done a stereo install in my previous vehicle (2005 Honda Pilot) I was confident I could handle this one as well.
For me, the most helpful post here in the ROC was this one:
http://www.ridgelineownersclub.com/f...ad.php?t=45100
Anything that I haven't described or shown here ... is in that post.
FULL PROPS to @Razorback92 for his work.

The before ... still has the label on it (and it still does)

The materials ... I love Crutchfield. Such an awesome resource. Select your equipment, and they'll tell you what additional things you need (helpful if you didn't know you needed it!)
The most valuable tool I used in this entire process was a lighted pick up tool. I used this for pulling every single wire through a spot that I didn't want to have to take apart. You can see one here: http://tinyurl.com/pv2a4oo
The second most valuable was a telescoping magnetic pick up tool - very handy for when you drop the very last screw of the entire project into the backside of the dashboard. Yep. I did. http://tinyurl.com/n9s96a3
NOTE: For popping the dash off, first remove the tiny tab on the top of the steering column. Make sure the parking brake is set, and then push the ignition key down into that hole. This is the lock for the gear selector, or "Prindle" as my younger son always calls it (P-R-N-D-L)
While pushing down with the ignition key, move the gear selector all the way to the lowest position. Then it's out of your way.
Use a panel removal tool (or something as nondescript as a butter knife) to pop out the tabs on one side of the dash. Once you can get your fingers in behind it, you're home free. There are eight wire connections on the dash that you will have to remove before you can lift it up and out of your way.
I used Razorback92's post to figure out where to run the power line for the amplifier through the firewall, so use that link above for reference. His explanation and photos are top rate.

I eased into it with the left rear door. In this photo I haven't removed the handle yet. The plastic liner comes off very easily when the car is new ... I did not have to peel any adhesive off at all.


Right rear door, with the plastic liner still in place
Factory speaker on the left, replacement on the right

Any difference? Uh ... YEAH!!!

I used the brackets sent to my by Crutchfield as a template to mark where I had to drill holes for the new mounting screws.

Made a paper template for the spot where the speaker gets installed

After drilling the holes, I installed some Dynamat to size in that spot, then opened it up for the speaker to fit.


The mounting brackets that came with the speakers ... I busted them apart and took the nuts for use to attach the speakers to the mounting brackets Crutchfield sent me. Ultimately I had to go to Home Depot to get some machine screws that were about 1/2" longer, but the mounting worked perfectly.

New speaker installed, Dynamat had to be notched out as shown because the back of the door insert has a large plastic form that fits into that spot.
Old Tweeter, new tweeter, ... oh boy. What to do.

I really wasn't wild about the idea of cutting up the manufacturer mount to attach an aftermarket speaker, so I found a different way around it.
I used my power sander to sand down one side of the speaker mount for the new tweeters, and then inverted it and attached it on the back side of the manufacturer grill. I used electrical tape to hold the tweeter in place, then slid the speaker mount over that - and it was so snug nothing is moving.


Back seat removed, revealing the box holding the factory "subwoofer" ...
Wasn't long after removing this that I realized my plans for the subwoofer were not going to work. I have my own woodshop and could easily have built a custom subwoofer box to fit, but that became a function of time. I wasn't willing to leave this project unfinished for the time it would take to get that done (I work 1 full time and 2 part time jobs, so this project could not linger unfinished).
I stole an idea from another great post here - putting the antenna behind the cyclops brake light on the back of the cab.
http://www.ridgelineownersclub.com/f...ad.php?t=34647
I used the aforementioned lighted claw pick-up tool to effectively push the antenna wire into the cab, up above the roof liner. From there I could pop the liner down, reach and grab the wire, then pull it in and run it over to the side, down behind the pillar cover, and along the floor on the passenger side, bringing it up into the dashboard behind the glove box.
I posted a question last weekend in another thread about what to do as far as the driver's door -
http://www.ridgelineownersclub.com/f...ad.php?t=68306
All the wiring for that door is in a Schoshe harness, and I wasn't sure what to do. After getting a few responses, and thinking about it, the first thing I did was cave to practicality - and take the driver's door off. It wasn't hard; five bolts and you're there.

With things exposed, it was much easier to get access through the rubber grommet, and get two speaker wires run through from the car's interior (one for the door speaker, one to attach the tweeter to that speaker).


After looking at the connections in the clips, I was able to figure out where I could go through these harnesses rather than try to go around them, or drill other holes in the door. So that's what I tried.

On the door side, I drilled holes through the plastic harness at the points where I have arrows showing on this photo. I did not contact any of the existing connections, and was abie to get the speaker wires run directly through into the door.
If you are using small enough gauge wire, you should be able to run both wires (speaker and tweeter) through the spot where the black arrow is.
NOTE: Where the white arrow is, that's actually where the bottom clip for the harness locks in place. You probably should try to run a wire through there. I figured that out after the fact, and just tried to force it back into place rather than start over. Fortunately, I got away with it, and everything fit back together properly.
A brand new 2013 Ridgeline RTL should have a better sound system than a 160 watt 6-disc CD change ... and since I had done a stereo install in my previous vehicle (2005 Honda Pilot) I was confident I could handle this one as well.
For me, the most helpful post here in the ROC was this one:
http://www.ridgelineownersclub.com/f...ad.php?t=45100
Anything that I haven't described or shown here ... is in that post.
FULL PROPS to @Razorback92 for his work.

The before ... still has the label on it (and it still does)

The materials ... I love Crutchfield. Such an awesome resource. Select your equipment, and they'll tell you what additional things you need (helpful if you didn't know you needed it!)
The most valuable tool I used in this entire process was a lighted pick up tool. I used this for pulling every single wire through a spot that I didn't want to have to take apart. You can see one here: http://tinyurl.com/pv2a4oo
The second most valuable was a telescoping magnetic pick up tool - very handy for when you drop the very last screw of the entire project into the backside of the dashboard. Yep. I did. http://tinyurl.com/n9s96a3
NOTE: For popping the dash off, first remove the tiny tab on the top of the steering column. Make sure the parking brake is set, and then push the ignition key down into that hole. This is the lock for the gear selector, or "Prindle" as my younger son always calls it (P-R-N-D-L)
While pushing down with the ignition key, move the gear selector all the way to the lowest position. Then it's out of your way.
Use a panel removal tool (or something as nondescript as a butter knife) to pop out the tabs on one side of the dash. Once you can get your fingers in behind it, you're home free. There are eight wire connections on the dash that you will have to remove before you can lift it up and out of your way.
I used Razorback92's post to figure out where to run the power line for the amplifier through the firewall, so use that link above for reference. His explanation and photos are top rate.

I eased into it with the left rear door. In this photo I haven't removed the handle yet. The plastic liner comes off very easily when the car is new ... I did not have to peel any adhesive off at all.


Right rear door, with the plastic liner still in place
Factory speaker on the left, replacement on the right

Any difference? Uh ... YEAH!!!

I used the brackets sent to my by Crutchfield as a template to mark where I had to drill holes for the new mounting screws.

Made a paper template for the spot where the speaker gets installed

After drilling the holes, I installed some Dynamat to size in that spot, then opened it up for the speaker to fit.


The mounting brackets that came with the speakers ... I busted them apart and took the nuts for use to attach the speakers to the mounting brackets Crutchfield sent me. Ultimately I had to go to Home Depot to get some machine screws that were about 1/2" longer, but the mounting worked perfectly.

New speaker installed, Dynamat had to be notched out as shown because the back of the door insert has a large plastic form that fits into that spot.
Old Tweeter, new tweeter, ... oh boy. What to do.

I really wasn't wild about the idea of cutting up the manufacturer mount to attach an aftermarket speaker, so I found a different way around it.
I used my power sander to sand down one side of the speaker mount for the new tweeters, and then inverted it and attached it on the back side of the manufacturer grill. I used electrical tape to hold the tweeter in place, then slid the speaker mount over that - and it was so snug nothing is moving.


Back seat removed, revealing the box holding the factory "subwoofer" ...
Wasn't long after removing this that I realized my plans for the subwoofer were not going to work. I have my own woodshop and could easily have built a custom subwoofer box to fit, but that became a function of time. I wasn't willing to leave this project unfinished for the time it would take to get that done (I work 1 full time and 2 part time jobs, so this project could not linger unfinished).
I stole an idea from another great post here - putting the antenna behind the cyclops brake light on the back of the cab.
http://www.ridgelineownersclub.com/f...ad.php?t=34647
I used the aforementioned lighted claw pick-up tool to effectively push the antenna wire into the cab, up above the roof liner. From there I could pop the liner down, reach and grab the wire, then pull it in and run it over to the side, down behind the pillar cover, and along the floor on the passenger side, bringing it up into the dashboard behind the glove box.
I posted a question last weekend in another thread about what to do as far as the driver's door -
http://www.ridgelineownersclub.com/f...ad.php?t=68306
All the wiring for that door is in a Schoshe harness, and I wasn't sure what to do. After getting a few responses, and thinking about it, the first thing I did was cave to practicality - and take the driver's door off. It wasn't hard; five bolts and you're there.

With things exposed, it was much easier to get access through the rubber grommet, and get two speaker wires run through from the car's interior (one for the door speaker, one to attach the tweeter to that speaker).


After looking at the connections in the clips, I was able to figure out where I could go through these harnesses rather than try to go around them, or drill other holes in the door. So that's what I tried.

On the door side, I drilled holes through the plastic harness at the points where I have arrows showing on this photo. I did not contact any of the existing connections, and was abie to get the speaker wires run directly through into the door.
If you are using small enough gauge wire, you should be able to run both wires (speaker and tweeter) through the spot where the black arrow is.
NOTE: Where the white arrow is, that's actually where the bottom clip for the harness locks in place. You probably should try to run a wire through there. I figured that out after the fact, and just tried to force it back into place rather than start over. Fortunately, I got away with it, and everything fit back together properly.