Depending on whether you want a box or cylinder, and depending on what you want to spend, I can strongly recommend the SVS PB1-ISD, which is their "smallest" box sub. It still packs a huge punch.

Of course, they have bigger, stronger offerings if you want to pony up the cash. But, honestly, I bet the PB1 provides more bass than most normal-size rooms would need.

Good luck and enjoy the system.