I was going down the same path, and went through Theta Intrepid, Proceed HPA, and EAD PM2000. Some of the amps I've used were pretty good. But they didn't provide the very last few bits of the musical satisfaction, namely the presense, detail, and the feeling that "you are there". Somewhat understandable, as the multi channel amps are targeted mainly for HT. The vast majority of HT users (there are exceptions, such as I am) are either not interested in high res music, or don't listen to music critically, and the multi channel amps reflect that.
An alternative path that I'm taking is two chassis system that consist of a two channel amp and a three channel amp. Or you can use three two channel amps, or five mono blocks, or what suits you. The point is there are much more selection available _way_more_, if you go this route. The downside is more rack space, potentially inferior voice matching among the speakers.
I currently have Pass X3 for three front channels, and Aragon 8002 for the rears. The current set up is much more musically satisfying than any other 5 channel amps that I had in my system. My rear speakers are already mismatched from my fronts, and considering how much musical information comes out of the surround speakers I really don't care about front / rear mismatch. I would eventually get a Pass X.5 for front left/right, and set up X3 to power the center and the rears. The slight mismatch between the center and the fronts is still not too important because the center speaker is already mismatched. It's from the same manufacturer but not an identical speaker. Even if I use identical speakers all around, the room acoustics will throw in some variation in the sounds coming out of the speakers.
If you are truly concerned with voice matching all the speakers, you can use a processor utilizing Audyssey RoomEQ instead of trying to match it with a multi channel amp. Audyssey will do a much better job, plus you get to choose your favorite two channel amp for music.
