Thanks everyone for the wonderful responses.
One thing I have decided is that I am moving up to medium format, and probably 6x4.5.
I am in a darkroom class right now (good way to see others' work), and the medium format negatives and prints simply don't compare to my dinky 35mm negatives.
While square negatives (6x6) are quite nice, I think I am more of a rectangular guy.
Now to figure out which camera...