What to use - a McIntosh MC202 or a MC7300?

Not sure you going to hear the difference with the larger MC7300 to power the
rears. I would go with the MC202.

I have 250 watts Musical fidelity amp on my fronts. And 100 watts on the center
and rear channel.

I would think the MC1's would be harder to drive than your center. Keep the 2 MC352's to power your front and rear and mono the 202 for your center. The MC202 would be a nicer match as it uses the newer end caps that would align with the MC352's, plus it is in the same series as the MC352.