Can my MC275 power speakers with 91db sensitivity

So, to be completely open kimono here, my experience that I refer to above is based on the following experiment. I would submit that this A/B test surpasses many in terms of relevance. That is, I speculate that many audiophiles compare memories of sounds of systems or components and in different rooms, dealerships, or other places. To be true, you have to minimize the variables and time between auditions down to minutes or seconds, NOT days or weeks. As an example, I read various audiogon members saying a certain CD player sounds better than another. I would place more trust in their assertions if they had both CD players attached to one preamp, simultaneously, with the same cables, with the same CD queued up and playing in time, to the same speakers, in the same room. I have done this experiment, many times, and I can tell you it is very hard to tell the difference. Otherwise, we are relying on memory, biases, and corrupted senses.
So, back to the discussion. I had my MC240 and C22 vintage equipment, which has been maintained, connected to a pair of B&W 804 diamond loudspeakers, source Oppo BDP95 from the RCA outputs. I had the same SACD/CD player connected simultaneously via the balanced outputs to a Bel Canto Pre2 preamp feeding an ARC 100.2 amplifier into the same speakers. To do the A/B, I would simply disconnect the banana plugs from one amp into the speakers to that of the other amp and play the same music from the CD player. Music from the CD player was in 15-30 second samples. So, the brain only had to remember sound from about 30 seconds ago, in the same room, with the same speakers, with only different electronics. Room was about 14x24x8 feet, perfect rectangle with only one open hallway (3 feet wide), system on the long wall, with basic treatment (curtains and no-name echo busters).
The differences were miniscule, with the only ones being mostly attributable to power - that is, at higher volumes the 100 w/ch amp could do better. Otherwise, both sounded very good and very similar. The only noticeable difference was that the ARC had better bass control over the B&W's than the MC240. The Bel Canto was also more transparent than the C22. The Mac combo vs the SS combo was just as good in the highs (treble).
So, this is but one example/experiment in terms of two different sets of electronics - obviously there are countless other components that one could purchase and do a similar experiment. The results I observed are but a small percentage of the possible outcomes.
Lastly, I would apologize for 'hijacking' this thread to get on the above soap box. But I think it is still relevant, in terms of when it is asked "can X amplifier power Y speakers", one notes that the room dimensions and characteristics of the components (efficiency of speakers, power of amplifier, etc,), type of music, and other associated audiophile pitfalls that I am trying to address here.

Thanks Al, I guess I won't be doing that anymore ! Elegal, regarding your last post, your description of what you are looking for is very well said, and coincidentally mirrors my own. I have only heard SF speakers in the stores (never at home), and they always sounded great. But also I would highly recommend you check out Harbeth SHL5 with your amplifier, as well, before you pull the trigger. Highly engaging, musically. Best of luck.

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.

Elegal, I am saying that they sound very much alike, in my experience. Which, you could argue supports Polk432's assertion that the Macs sound like SS (or, my SS amp sounds a lot like tubes !). My point, and I was not trying to beat up Polk432, and it was laced with a small measure of sarcasm, is that people talk about great differences between electronics but ultimately if they are well engineered they should not sound that different, aside from differences in power (power requirements of the associated speakers and room) and other inter-component electrical characteristics. My secondary point is that if components do sound very different from each other, then perhaps one or more of them is flawed in some way (from some reference), perhaps built for a specific purpose, compatibility, and/or sound, which if used outside of those parameters might sound horrendous.
Speakers sound a lot different from each other, however, in my experience. I would consider the room, then match the speaker, then match the amp, then the rest...