From everything I've read, that seems to be an excellent suggestion by Wid.

I had my Sony SAWM40 (120W) in a room that had the same volume as yours. The bass was simply gut-wrenching in that little room . So my opinion is that you don't need a lot of power for that room volume. Try to find a sub that is musical. You will have to try it out in your room and should not rely on what you hear at the shops.