Hey Fowl, did you have a budget in mind....?
Thats a pretty small room, and lots of subs out there would be more then ample.
For tons of output in a small room, the SVS SB12+ would provide tons of bass with a bunch of features for room integration as well...
Really small footprint, and output that will certainly impress.
Just one of many many subs out there, and I'm sure you will get plenty of suggestions..
**** Oh forgot to add, they have a special right now... *****
* For a limited time, try an SB12-Plus for 45 days. If you aren't thoroughly impressed with its performance, SVS will refund your purchase price... including shipping!