If you have a cap use it. You can never have too many capacitors. As far as hooking up your amps you could use "y" adaptors. I would use the rear channels and split into my sub amp. JL subs are my personal favorites, I had two 12w1's in a sealed box with 800 watts of power to them and I couldn't get them to blow...I couldn't even get them to bottom out, and they were rated at 150 watts max! The w3 subs are a very good choice
