I have the dayton UM 15, and I would consider another sub. Its not very defined, and sounds muddy above 50hz. Great for sheer output and depth though. I would try the dayton reference series for half the price. They likely play higher up and might be tighter.
Well that isn't very encouraging....
The reference series just doesn't seem "beefy" enough, but I certainly don't want "muddy", especially in the range I am trying to improve in the first place...