do what I did and rip out your rear seat and slam in 4x 10w7's
my honest opinion is get 2x 10w3's and a 500/1 but i would stay away from 13's as opposed to 2x 10's or even 2x12's if you are really feeling adventurous
I'm assuming you want the shallows for an under-seat box, but having a smaller box in the back isn't as bad as you might think it is, unless you are driving a busload of people all over the place... flipping up the passenger back seat gives you more then enough room for a half decent system to be installed and secured properly.. I'm partial to JL's as you may have guessed, but there are a lot of quality setups out there, check out DIYMA (do it yourself mobile audio) forums, and welcome.