For SQ, as the person above me stated, a sealed 12 is usually a better and cheaper route than anything else. A friend of mine has a single Type-R 12" in a (very) small sealed box in his trunk of an older acura. The bass isnt audible outside the car (wont get his stuff jacked) but inside the car, it gives clear, crisp, deep bass. Two 12s, if you want a balanced sound through mids and highs too, will probably be overkill.
Brands for SQ... I would recommend massive audio and pioneer. Pioneer has some good 12s with single voice coils, which is fine for SQ. Massive audio low-end will give you enough power and SQ.