Oops, I just noticed this request for a response. (Thanks for filling in Dan!). What I expected is to hear and/or feel more bass. Sure, I get that in spades, but it also seems to me that the sounds top to bottom, even the treble, seem to have more of a foundation when the sub is on. The note coming from a violin seems a tad more solid, more real, with more texture. This is the furthest thing from my expectation of what I'd get from a sub that I can imagine. I don't know a lot about the structure of music - is it possible that there are "overtones", or some content of the bass response that really does reinforce higher frequencies? (legitimately, not in terms of artificial coloration).
Art
Art