it comes down to a system that I can tolerate in the smaller room and that excels in the larger room.
This concept is difficult for me to fathom. It usually takes me a month of weekends to get a system dialed-in for a given room. Once it’s performing at its peak, I don’t want to touch a thing! At least not for a long while. I can’t imagine rotating a system across three different rooms.
Minimally, I would purchase three pairs of loudspeakers, once that will perform optimally for each room. Matching amplification to the loudspeakers is also important, so I might also purchase dedicated amplification for one or more rooms.
I’m at a loss for how to help, but perhaps our exchange will be informative to others here. Good luck!