I haven't heard the other 5 on your list, but I can tell you that the B&K Ref 50 is probably not up to par. I had one shortly(about 3 weeks) as a loaner while I was waiting for my pre/pro and I didn't even like it for HT. It was noisy and somewhat compressed and dark sounding.
I have heard lots of good things about the Bryston, especially for music.
Another pre/pro you should consider is a Proceed AVP2. I know Proceed is not around anymore but there was NEVER any issues with the AVP, and if you buy one from a dealer that still has them, you're at least somewhat covered. I had the original AVP for about 4 years. While IMO, HT processing is not up there with the best, Lexicon, etc.. 2 channel was outstanding.
I have heard lots of good things about the Bryston, especially for music.
Another pre/pro you should consider is a Proceed AVP2. I know Proceed is not around anymore but there was NEVER any issues with the AVP, and if you buy one from a dealer that still has them, you're at least somewhat covered. I had the original AVP for about 4 years. While IMO, HT processing is not up there with the best, Lexicon, etc.. 2 channel was outstanding.