Just installed the jvc cs-bb2 6" amplified sub, it goes underneath the driver's seat and works pretty good for what it is. i think its a good mod for people who want a little more thump than what the door speakers provide and leaves you all the space in the trunk still. oh and it's only 150$ so its pretty cheap too!

 

manso:
Do you think it would fit under the passenger seat also? Then you could run two of them.

 

nope it won't........... tried it. oh update with a little more tweaking its sounds better but definitely not for hip hop or r&b music you can't get that rolling bass feeling.