I am curious about the benefit of multiple subwoofers. I have one 10" Infinity Perfect in a sealed 0.6 cubic foot box, with about 275 or so watts RMS running to it. I can't imagine having much more bass that that. It hits pretty hard, is quite loud, vibrates everything, and will "boil" the water outside up against the hull. I find myself having to turn it down frequently because it can become too much, and, well, my fiance gets pissed too.

So I am asking the stereo expert guys like Phil and David and Brian how much having more can affect? If I have one amplified sub that plays at a certain loudess (just going to throw a number out here, say 100 db) if I double that to two subs I definitely don't have 200 db, so what is the benefit?