Can my MC275 power speakers with 91db sensitivity

I couldn't find an impedance curve for the Olympica III, so I'm not sure. But given its 4 ohm nominal impedance and sensitivity that is similar to the Cremona (1 db is a trivial difference, and in this case is in the wrong direction), without further information I would not have confidence that it would be a good match.

To be sure it's clear, everything else being equal a higher sensitivity (defined as SPL as a function of input voltage) would work in your favor. Note that the negative reference to greater sensitivity in the John Atkinson statement I quoted referred to sensitivity to amplifier choice, not to SPL sensitivity.

Also, I see that the Olympica III is listed at $13.5K. There are lots of good choices in that price range which can be confidently predicted to be good matches, including models from many of the manufacturers I mentioned above.

Regards,
-- Al

Remember that the 75 watt rating is conservitive on the Mac 275. It's more like 90.

I listen to type of music and the mc275 has no problem powring my Dynaudio c1 signature 85db/1watt sensitivity

Polk432, the MC275 sounds more like solid state than tube? You mean that those Binghamton NY engineers from 1960 found how to make modern SS sound with tubes, only for modern tube amp manufacturers to go back to...tube sound? And in 1970 when McIntosh moved to transistors and everyone said they sounded terrible, they just got SS wrong? Sorry, not trying to be a jerk, but (as I have posted here and elsewhere) when I read a review about the greatest new SS amp that "sounds amazingly like tubes" and the greatest new tube amp that "sounds amazingly like SS" it makes us all sound crazy. One interpretation, as others have made, is that tube amps have high amounts of harmonic distortion. And therefore, if a tube amp from 1958 sounds like SS perhaps they were well manufactured and accurate instruments. Audiophilia...

I should add, I realize that the OP has the latest model of the MC275. In which case I second what I said above - "tube amps sound like SS." Then why buy tubes when you can buy SS. By the way, I'm running a 'vintage' MC240 right now, and have had side by side an ARC SS amp, and have trouble telling the difference between the two amps. Perhaps a well engineered amplifier sounds like another well engineered amplifier.