I installed a Pyle Hideaway 8 inch sub in my truck in the same location as your Kicker. I think the Kicker is only rated at 150w max, the Pyle is listed at 600w max/ 300w rms, although the actual numbers are probably considerably lower than that. Even though it is probably putting out less power than what they list, it still shakes my truck when the bass hits and is an incredible upgrade to the factory Bose system. Overall, the system now sounds pretty damn good with the new sub installed. The key to getting it to sound good is getting the sound adjusted properly so the bass doesn't overpower the existing Bose system. It took me about a week to get the sound adjusted properly between the stock EQ and the subs bass controls.
The Pyle Hideaway 8 inch sub only cost $180, and for that price, I am very happy with it.