MC275 Tube Rolling...

For the KT88s the best I've found, and reasonably priced are the current production Genalex Golden Lion KT88. They are vastly superior to Russian Lyting "C"s, Electro Harmonix and the stock McIntosh tubes. There are several online sources for the Genelax tubes. Then, add Herbies tube dampers (to all tubes) to reduce microphonics and you've got a really dynamic, rich tube set. For the 12AT7s and 12AX7s you can't go wrong with either Mullards, Telefunkens or Amperex Bugle Boys. The Shuguang triple mica have also been recommended to me for the small signal tubes but I've not heard them.
I realize that McIntosh uses the stock tube sources to insure production supply continuity, but the tubes I mentioned above will transform the MC275 and bring it to an entirely different (superior) level of performance.
The 275 can also be further improved by setting it on three Mapleshade Heavyfoot V3 brass footers.

Lapierre makes an excellent point about matching tubes. Sound advice to follow.
I'm using a McIntosh C2200 as my pre and it is a great match for the 275 so I think your interest in the c220 is well justified.
I started on the tube-rolling path when I noticed my stock KT88s were pulsating blue light. It was weird because you couldn't see it looking directly at the tubes only out of your peripheral vision. I thought it was just my aging night vision until my wife noticed it, too. The stock tubes don't last more than a year, if that. But even if they're still good you will be rewarded with rolling to better tubes.