Here are a few pics of before, during and after. This is in a 2000 Celica. I traded the two 12" subs in for 1 12" and I think it sounds even better. The two that were in there before were crap.
Before
Finally Fit!
Finshed Product
Total this took me about 4 hours to build. There is room behind the amp and I mounted the 12 disc changer there, to access it you just have to drop the back seat. Since I dont really change the discs much this isnt a problem. I sealed all seams with silicone to prevent air leaks. All of the wood is 3/4 MDF and the carpet is just some fabric i picked up for $2/yard. the back of the box isn't carpeted but no one will ever see it anyway.