Personally, I've never been a believer in non-localized bass, until I read the theory that you place multiple subs around the room for the best bass response. Now, that seems reasonable to me. For music, I'd still run the HT3s full range for a more even distribution of bass. Currently, I have two subs, one spaced within a few feet of a corner on one wall and one spaced about midway on the other wall. I only have one working right now (5 month old + 3 YO = not much time), but I hope to have two working in a few weeks.
My main concern is not overdriving the drivers in the HT3s/HTC with low bass material they can't produce anyway. I'll have to see what the options are for my receiver and see if I can run each set of speakers at a different frequency range. I know my surrounds cutoff at 120Hz, and 150Hz (according to the auto setup program), but I'm not sure whether the receiver just applied one cutoff to all the speakers that are selected "small" or whether I can select different cutoffs. If I have to run the HT3s/HTC at 150 HZ, I probably won't do that.