I added a Bazooka 6" Amplified Bass tube behind the seat to replace the stock sub-woofer. All I can say is 'WOW', more than enough BASS for me. I love the clean install without losing any storage space. Install is straight forward if you buy the recommended cables. The rear seat hangs from two top brackets and is secured by bolts across the bottom. One person can easily lift the seat from the top brackets and lay it down on the floor (with seats up), and work behind it without removing it from the cab. I found it useful to follow these instructions...
1. Pull the plastic panels under the seat bottom straight forward to remove them.
2. Remove the six bolts (14mm) holding the seat and center seatbelt in place.
3. Pop the two small plastic covers at the top and behind the seat using a trim removal tool or screwdriver tip covered in masking tape.
4. Lift the seat straight upward.
The Service Manual states a 35 ft lb torque and must be re-installed in a certain sequence for the 6 seat anchor bolts (not the seat belt bolts). When putting the rear seat back in install the bolts in this order. (1) center left (2) center right (3) left lower (4) right lower (5) left upper (6) right upper.
Now this is what I'm talking about! I have looked through hundreds of pages to find this simple direction on removing the upper back seat. I'm going to assume this also means you can install a sub without tackling out the bottom seats! Thank you Heli I might actually do it myself now.