You present a good question and I feel comfortable offering some feedback. I have a B&K 507 S2 HT Receiver, which in its own right does a very nice job for 2 channel and HT. However, the configuration of this receiver for the zone 2 application required me to have another amp to drive the zone 2 speakers (or wait over a month to have my 507 shipped, modified and returned).
As a result, I purchased quite a few used amps to determine what I wanted. In the end, I purchased a Conrad Johnson MX5600 5 channel amp. I bought this because I like the flexibility it offered for the second zone and if I really liked the sound, I could use this to drive the main speakers in my HT. This is how it is presently operating, to my great pleaseure.
Because the other amps I was auditioning were only two channel amps, I am hard pressed to comment on too many other multi channel amps. FYI - the CJ SS amp is running Totem speakers (Arros in one room and Hawks in another). Because I am awaiting delivery on some new (used) VR 4JR speakers, I may once again be in the market for another amp just for these speakers if necessary. Anybody looking to dump a Plinius, Sim, Krell 400, Arye for very cheap? Give me a call.