[Crash ?]

hhmmm...

The fact that you WANT to be able to remove the sub box when you need some space says something here and gives me an idea and a way to kill to problems at once.. Mounting the amps and the fact the rear seats don't fold flat..

Build a platform the size to the cargo area to set the sub box on and the amps under.. Since the amps will somewhat confined, you may need to go ahead and think about installing cooling fans..

You can remove the sub box when you need space and you can lay the seats down and not have to worry about laying anything on the amps either..

I have this feeling it the amps are to large to bolt on the back of the seats, they will be to large to fit under the kick panels where the Monsoon stuff would go..