If there's any way you can swing it, try and get at least a single 10" subwoofer in there somewhere. You don't have to fill your whole trunk with sealed boxes or anything like that. A free air sub mounted in the trunk playing right through the seatback of the rear seat might work just fine, and will add immeasurably to the quality of your sound.

tanstaafl.

"There Ain't No Such Thing As A Free Lunch"