Today I found some spare time and put the back wall carpet back in, cleaned up the wiring (still some work to be done) and put the sub in the box, cone outward. Sounds like poop, not enough box space. It's going to be inverted again, which means that if I'm going to have the sub in my setup inverted, I'm going to go all out. So I'm planning a new build for the future...
-1.99 ft^3 box to take up the entire space behind the rear seats. 15" tall, 50" wide, 5" top, 8.5" bottom. Sub firing inverted between each bucket seat.
-AQ HDC310 sub, since they're on sale for a sweet deal.
-Amp will stay until I have more money.
-Arm rest between the seats, connected to seat brackets. MDF on bottom, connecting to brackets, then another sheet of MDF above that, where the amp will be held. Then a sheet of plexiglass on top of that to protect it. At the rear of the arm rest will be a plexiglass "shield" that will mainly serve the purpose of protecting the sub from being removed.
I'm excited, but need to start learning how to cut wood and make boxes or else there is no way I will be able to afford this.
Edit: Either that, or just wait and do a blow through way down the road.