I did this mod a while back, but figured some people might be able to use it if you are trying to keep a mostly stock look but add some bump in the trunk.
2007 SR5 V6 w/o any special stereo system. You know that place where the stock sub goes? well, if you do a little trimming it can fit some decent quality amps.
I fabricated the metal pieces from strips bought at home depot and padded the amps against each other with some packing material. These are pretty large amps, the results:
1x 450/1 JL Audio amp for front and rear. 19.7" x 9.25" x 2.36"
1x 500/1 JL Audio amp for the 12" sub i have in the back. 13.4" x 9.25" x 2.36"
View attachment 182329
View attachment 182331
Excuse the dirt, I generally keep a mountain bike in the back of my car. hah.