that looks pretty clean.

 

mine's hidden under my driver's seat. you can barely see it its a good spot. In my last car I had it mounted behind the rear seats kinda like that too. no pictures :/

 

i have one under the driver seat and one under the passenger seat, i'm short so i scoot my seat up and you can see half the amp, but if you have long legs and scoot your seat back some amount you can hide it. I have tinted windows so you can't see my amp anyway.

Here's another idea, but expensive:
http://forums.nasioc.com/forums/show....php?t=2112155

 

i got one of those audio innovation amp racks.. honestly, i want to mount it elsewhere so that i can get an X-brace in there or a rear strut tower bar. i suppose if I weren't too lazy, I could cut some holes into the rack so the bar could fit.. but it sure is too pretty to do that.