The UFW is 500 watts, ULW 350. The UFW has a single band parametric EQ to flatten the largest hump in your bass response, and allows for bandwidth adjustment. The ULW uses an auto-type EQ that picks it's own setting, and cannot be bandwidth adjusted. Also the UFW has the traditional Rocket finish with the piano black top and bottom. For a room your size I'd look at minimum the UFW-10, perhaps two of them. Of course, it depends on your preference for how loud you like bass, in which case neither one of these are going to give you high SPL's. They are tight and tuneful though, and that is why I like mine. It will kick for HT, but not like two of them, or even a 12" sub will.
You could always add a second UFW-10 down the road should you need to for HT use.
Ed
* Sierra-2EX's W/V2 crossover upgrade
* (2) Rythmik F12's
* Parasound Halo P6
* Audio by Van Alstine DVA-M225 Monoblock Amps
* MiniDSP 2x4HD For Sub calibration
*World's Best Cables Canare 4S11 speaker cables