You'd be better off with tens or eights, so you can keep a rear firing enclosure. A single twelve might work. Just get something beefy, a nice box design, and throw gobs if power at it.
My vote is for a pair of nice 10s or a single mean azz 12"........My original setup was a single Havoc 12" in 3 cubes with 1600 watts and it was nasty loud and sounded amazing while doing so....Good luck OP