Building a well, need advice

Hey guys. My plans of purchasing the Civic fell through. I've still got my saturn. So, i am going to build a wall beind my front seats. This will be my first attempt at something like this so I have alot of questions. First, and foremost, for the actual wall piece, could I use plywood? I know plywood is not good for enclosures, but I figured using it is the WALL itself it should be good enough. I am going to go to the hard ware store tomorrow and buy my MDF for the boxes. I am going to make about 1.25cu ft per sub. How do I go about keeping the subs suspended in the air? Will I need some 2x4s to hold them up? or what do you do? Does anyone have any build schematics or pictures that i can look at? I have three subs, and I'm not sure how I want to place them. I think I am going to have 2 facing normal, then the middle one will be reverse mounted. I know how to wire that, but I was just wondering how much different of an air space that sub should recieve than the 2 mounted normally. my brain is fried, thats all i can think of right now. Im sure ill have more questions soon.