i wouldnt do any thing more then 1 10" or 1 12". I spent maybe $400 in total on my sound system including my 10, 450watt amp, my 6.5"s front and rear and my tweeters up front, and my car sounds just as good or better then my roomates BMW that he spent $3000 worth of JL audio stuff in. He is running 3 JL 8" subs in a box, and his car is honestly the most anoying thing to ride in. If you just want the bass sound and actually enjoy your music, i would say 1 good quality 10 or 12 with a good amp...but if you wanna b heard from a mile away, then go with somethin bigger. I have a single 10" pioneer in my trunk hooked up to a 450Watt sony amp in a sealed box, and it delivers enough punch. Even in my gf's coupe, we have an 8" Basstube and that provides enough of a punch too for listening and enjoying music. I guess it all depends on what type of music you listen to and how much bass you actually wanna be making. I personaly like it when i can hear every note in the song as compaired to just the thuds of the subs and hearing the ocational high note or vocal.
EDIT: mine..i know its in a hatch, but it delivers enough of a kick

i know..messy trunk
This post has been edited by Valo666: Oct 7, 2007 - 2:58 PM