Any one running four 12's?

[tyler]

I'm stepping away from engine work for a moment and decided a nice sub set up would be a vgood change of pace. I have my plan all drawn out, measuments done, checked and checked again and decided on a fiberglass box with mdf framing. Now I've been building sub boxes since I got my license and have picked up a good amount of skill, at least with car trunks. I will be running 4 diamond audio 400watt 12's off of 2 jl amps that are rated at 500 rms true watts. My plan is to mount the subs up but slightly slanted so they all focus and the middle of the hatch and port the box towards the rear, roughly the area of the spare tire. My question is if any one has this many subs, is there a difference in acustics of the car since there is no barrier (ie seats) in the way? And wll this sub port set up be optimal?
As always thanks for ur input and any suggestion is welcom. But I am sticking with the diamonds and will upgrade to higher watt diamonds later on.

Tyler