You could always rent a Mamiya 7 for a day to see how you get on. On the other hand, they do keep their value, so you could also buy one.
I recently fell for a Rolleiflex TLR 2.8, and was astonished by the fact that just that single camera seemed sufficient. It produces great results, and the format at 6x6 is great. But I still have a 645 system as well (Pentax though).
Did consider the Mamiya 6 or 7 but its reportedly harsh bokeh has made me doubt. That may be something to consider. Sharpness of the 80mm lens is, they say, unrivalled.
Still, I really love carrying just my Rolleiflex.