One alternative that may exist for you is to solicit an ULTRA amp owner who live near you to bring their amp over for a comparison to the MC 275 / demonstration. Frank's customers are a lot of his sales force, and I think they'd be happy to do this kind of thing.
I have compared the two amps, and each has its strengths. To me, the Ultra 550 sounds more detailed and muscular. The bass control goes well beyond what the MC 275 can do. The Ultra 550 can drive just about anything, using any kind of music
In the MC 275's favor, in my room it presented a larger soundstage, more height, width and depth, when the discs that had such information. If you have speakers that don't require a lot of power, or you listen mostly to jazz, it could be a tossup.