I guess I'm a little late to this clambake but I shoot a lot of 6x6 so I thought I would chime in. I seem to be lucky when it comes to procuring cameras; I have a Graflex 22 that I think I paid $20 for (including the adapters that allow me to use 35mm in it, though I have never done it), and it's a cute, light little thing. Yes, it has a 90-degree film travel, it doesn't automatically cock so you have to either look through the red window or guesstimate where the next frame is, no interchangeable lenses... but it does give nice sharp pictures and it's light. I also have a Mamiya C2 that has winding issues, and two C220s that are bombproof -- the interchangeable lenses is a great feature and the lens quality is unimpeachable.
But these have been sitting on my display shelf for quite some time, because I was given two Norita 66 bodies and a bunch of lenses some years ago and after sending them away for repair, they have become my go-to 6x6 cameras. It's also got a very fast normal lens -- 80mm f/2 instead of the 2.8 that most MF cameras use, so that lets me walk around a little longer before I have to put it away in the dark. Image quality is very good, too. The Norita is an SLR so it handles like an SLR, though much larger, and it's a great street photography piece when I have the waist-level finder fitted. I think the most fun thing about the 66 is that it's very rare; I get stopped on the street when I walk around with it, and it starts a lot of conversations.
If an SLR is more what you want -- though it sounds to me like you have plenty of toys to play with -- you might consider one of the German or Russian ones, like a Pentacon Six or a Kiev-60. They can be had cheaply, and from what I understand the Pentacon Six lenses will fit the Kiev. Just have to make sure that you get a good copy of the Kiev as the Soviet stuff can be balky or have quality control issues.