Hey Phil - in my room I really don't need a sub or center for the Micros. They get into the upper 30Hz range, and the mid-range is so spot on, I really don't miss the rest of the bottom octave.
Ohm does make a center version of the Tall with the tweeter facing more forward. I've heard that it makes a better center channel than the center channel that they make for their sub/sat system. I dig the front to back depth of the Ohms, especially with dialogue - really gives you sense of where the actors are, spacially.
Now that we're talking about all of this HT, I guess an Ohm Walsh HT system would be pretty nice. My main thing with speakers in general, is that I feel most of the time they're firing right at you, which really doesn't feel like a musical experience to me. Center channels and surrounds only add to this effect, so I find most HT pretty fatiquing. But like I mentioned before, I've heard some good ones (sounds like you have a nice set-up) and it can be a serious charge!
The larger Ohms don't need a sub from what I understand. Walsh series speakers are known for their bass performance, and even my little Micros fill the room nicely. Ohms really energize the room with sound, so I don't even miss the sub (although with all of this talk, maybe I'll grab the sub from the bedroom system and give it a try!).
My room is borderline size between the MicroTall and the 100s. I figured with the return policy that I'd start small and exhange if needed. When I find myself in a larger room, I'd like to try a larger model. In the meantime, I'd like to try an AVA amp with what I have. I also have a feeling that Frank's gear will synergize nicely.