Check the SVS SB12-Plus subwoofer; it's a sealed (closed enclosure) sub.
Or for a ported (vented) one, look at the SVS PB10-NSD.
And, check the HSU Research VTF-1 sub, and the STF-2 or the STF-1.
Also, have a look to REL T-1, T-2 or T-3.
* The Rel T-3 would do for the size of your room.
These are great brands for sub, and the'll do for your system and room's size.