It's always good to try what we have, and upgrade later if we think we want to.
If possible I would try to set the power voltage gains around 160w or less for the factory sub, just to be safe.
The video on the test done here shows about 260W with 4 ch bridged. Bridging just 2 channels should deliver similar power, either sub alpine or JL sub should work fine with 250 watts and will deliver way better sound compared to the factory sub.
I am going to go with the PN4.520D as it is way smaller than the P4.500 and gets good reviews.