Do you have a budget? Did you want two 12's just for the aesthetic purpose? Keep in mind that one sub is cheaper than two or one quality sub can be the same price as two cheaper subs. One sub usually will take up less space than two(if trunk space is important to you). Especially since you'll want to build a proper enclosure this time around.
Yes, you can build a ported box geared towards SQ, but the box is still dependent upon the sub. The general rule of sealed for SQ and ported for SPL seems to stem from the nature of prefab boxes in which case ported=crap SQ. Yes, ported will be louder, but built properly, they can sound great.
Just stuff to keep in mind.