sub(s)/amp combo will buzz a stock car if it's not soundproofed. Even then there may be small vibrations. I feel the rears add "fill". When you fade the rears out, it's not the same.

San

 

WRXs are tin cans

If you really want a nice full sound you MUST use sound dampening materials......and believe me....they do make a difference. Doing the doors will increase efficiency and improve sound quality. Doing the trunk will cut down on the rattling...but the really will depend on your sub and how much power you run.

About rear speakers.....

I've only heard a couple rexs and I have yet to hear one that has much rear fill. You will not lose quality by eliminating the rears since the fronts are what you should hear. I can fade halfway to the back and my front stage is still very strong.....so the rears hardly make a difference. You're probably better off eliminating the rears and spending more dough on the front stage and dampening (which can become costly if you do it right...believe me).

Amp.....

Under the seats are probably the best option...there is a TON of space under there.

Shoot me a pm if u want more info....i'll try and help

 

the sti spoiler will also help kill the natorious trunk rattle.

as for the amp yeah under the seat will do. i have a 9x16x2 inch amp under each seat in mine.

adding sound deading to my doors (inner and outer membrane) trunk and to my floor made my car feel heavier/solid. it didn't have that tin can feeling. hard to explain but it did make a differene in the overall feeling while driving besides the improved sound quaility.

 

While good speakers will definitely sound better than crappy ones....I believe you really won't get what you should out of them without any dampening in a rex. I guess it really depends on what you consider to be "good" (everyone has a different view on this)...but I think most components in the $350-400+ range would be a waste without any. There are some dampening options that don't add that much weight and dont forget about efficiency.

While the dampening will add some weight.....the increased efficiency may allow you to run less power (which usually means lighter, smaller amps) to get the same performance.

But hey....if you're a weekend racer I understand keeping weight to a bare minimum. If I could only explain how much of a difference the dampening made in my STI....but then again I drive about an hour a day and really care about my music

 

the sti has more than enough power for auto-x and good lap times will only come from experience and skills.

if you are into dragging then yeah weight is crucial but you will only be adding 10-15 lbs of sound damping just take out your spare tire at the tracks to compensate for it.

 

Ill bring the STi down to the dealer tomorrow when we check out that Accord and you can hear my system. The car does rattle. I have tried to track down as many noises as I can and fix em and have had limited success.

 

Try a 12". Hah. Glad I didnt get one. The enclosure they built would have taken too much room. Atleast now I can still get to my spare, barely tho...