I used to run one dual voice coil pioneer 12" behind the passenger seat, but it wouldn't sit flush.
Get the mtx box with the 2 10's in em. Plenty of backpressure, and there tuned for that box. Get an amp thats actually rated (RMS only, don't compare peak numbers) to what your subs can handle, and it'll be more than you need.
I run a pair of 10" JL Audio W0's in a series in a custom box with a kicker 250.2 wired to a single channel. It took alot of work to get the system setup to where the subs had enough volume in a sealed box but didn't take any of the leg room away (I'm over 6'6" tall) and still allowed me to stand my two 10lb nitrous bottles behind the passenger seat. You could put your amp where I had my bottles. I have my amp under the passenger seat.
I have 2 Punch 1's 10" in a box with exactly the right amount of air space running off of an Alpine 400w mono amp. It hits very hard. I have the bass turned down to a -5.