what you will want for a subwoofer is one that goes down very low in frequencies.
a short while ago i changed the tuning on mine from 16Hz to 11Hz, and i'm not going back to the former setting, it's so much better.
also, so far, the speaker in the sub has not bottomed out; it still has some in reserve.
when a movie does have info in those frequencies, it makes a very good addition to the movie sound, it adds to the movie feel as the director wanted it to be. LOTR and Avatar and others are better when those ulf are reproduced. WOTW's tripod emergence scene at the beginning of the movie makes your feet move with the waves in the wooden floor and... (enough said).
