I had the same priorities when building my system. I need my trunk space, but also wanted enough bass to satisfy me, just not overkill. Here is what I did and the seats still fold down.
The back of the seat is metal, at least on my 95, not sure about other model years. I used a spacer plate with 3/4" dense weatherstrip to seal the plate to the irregular surface of the seat back. I also cut the hole in the metal smaller than the surface area of the cone to give the sub some loading. This works well, if you do not have to have 140 db. I have a PPI 4200 amp running the entire system, and it is clean, tight, and loud enough for me. (high 120's)
One fifteen is probably around the same cost as 2 eights and more efficient.
Hope this helps.
-Scott
Originally posted by cthomp21:
I'll build it out of 3/4" MDF, liquid nails, pillow stuffing, automotive grade carpeting, etc... the usual stuff.
It will be dual-chambered and be mounted to the bottom of the rear deck. It'll be about 6" tall and will span the width of trunk necessary to provide the box volume I need.
The amp will be mounted on the face of the box. The subs will be bottom mounted to allow for maximum clearance under the rear deck. I'll cut all of the corresponding holes in the rear deck sheet metal and dampen/brace as necessary.
Yup, it'll be in my SVT.
Space is definately an issue. I travel a lot and need the trunk space. I don't like sub boxes rolling around in the trunk, and I don't want to lose any floorspace. I also don't want to make my folding down rear seats useless. I'll also mount the amp on the face of the box, so everything will be nice, neat, and tucked out of the way and still easily accessible. Also, I'd prefer subs firing into the cabin as opposed to trunk. I'm into efficiency and don't want to get into overkill to provide my system with some much-lacking thump.
I'm looking into 8" sub(s) as 10s require more space (box volume) and are slightly too big in diameter to fit into the configuration I'm contemplating.
You've got some ideas that are more off the wall than this one?????? 
[This message has been edited by 95TealSE (edited May 04, 2001).]