I just ran across a thread reviewing this guy
Boss Audio BASS600
Its an 8" Amplified Sub with remote gain control and all that. The reviewer made it sound pretty good, and Amazon has it rated at ~4.5/5 Stars!
Now 60% off
(115.05$ instead of 286$!)
Probably gonna get me one of these, they also make a 10" version (the Boss Audio BASS1200)