I recently acquired a Manfrotto 054 ballhead that works really well with my Mamiyas: RB67, 645 Pro and C330.

I have it mounted on a set of older, fairly heavy tripod legs that are a decent Chinese clone of a basic Manfrotto tripod. I'd like to upgrade the legs, but I don't really need to.

Probably the best advice I could give to you would be to decide first on a new head, and then go from there.