For that size room almost any 12" sub will do well. The PL-200 or a pair of Klipsch RW-12d subs. I would personally go withthe Epik Legend for that size room. I think a good sealed sub will do wonders.
I agree. A sealed sub would be my choice. Legend most likely. Tons of mid bass with the low end reinforced by the room.
Point blank....given the layout provided any 12" or even a good 10" will provide enough bas hat you desire. Will will just have to make a choice whats best for you & your budget really. Epic Legend is at $500, Outlaw Plus is at $500, Bic Pl-250 is at $260, PA-120 is at $220, PA-150 is at $360 and so on.