Wow, that is a pretty sweet install. I really like the sub in the spare idea, I have a stupid donut, but thats one more reason to get a fullsize spare. I've thought about putting an amp under the rear seat like that, but I'm concerned about it overheating with the lack of airflow.
I run a similiar setup with 2 amps under the rear "bench" which only looks like a bench because the oem upholstery is wrapped around a pair of 12"-14" kicker boxes (don't recall) whick include mid's and tweets with the tweets facing forward with the bench in it's normal position....I just took the upholstery off and cut up the foam so as to fit the boxes...Looks neat, no advertising but my occasional passengers hate me!
I run a similiar setup with 2 amps under the rear "bench" which only looks like a bench because the oem upholstery is wrapped around a pair of 12"-14" kicker boxes (don't recall) whick include mid's and tweets with the tweets facing forward with the bench in it's normal position....I just took the upholstery off and cut up the foam so as to fit the boxes...Looks neat, no advertising but my occasional passengers hate me!