[spinem]

no matter what you do you WILL HAVE to move the seat forward.
shallow mounts are eaaahh. alright.. theres a reason why all speakers are the size that they are, shallow mounts WILL sacrafice sound.

collapsing the steering shaft will give you more room yes, but at what point do you draw the line?

get some thin back seats and you will not have to make your own box.
if you dont know what your doing, and attempt to make your own box, it will sound like poop.

to all those who apposed my first answer, re-read. i answered correctly. WITHOUT hacking, modding and going out of your way, stock will be a cramped fit. sure it can be done to fit all comfy and roomie, its all a matter of time and $$.