y didnt you build a box for behind the seat ? i put two truck boxes back there and was gonna have my sirius setup (attached to a piece of 1/8" plywood) back there between them but i decided to sell the whole SIRIUS setup and just use my CD player (under my seat)
i did think about building a box for behind the seats with 2-10's but im not a big bass fan (i like but not that much). more than enough room back there for a box.
just curius since you loose all that floor space for any passengers (wife,girlfriends,buddies-both genders)