Can my MC275 power speakers with 91db sensitivity

I see that the amp is rated to deliver 150 watts into 2, 4, or 8 ohms in paralleled mono mode. So adding a second amp might very well be beneficial, but given the expense and the wait that would be involved, as well as some remaining uncertainty, personally I would look for a different speaker that has more benign impedance characteristics. Unless an audition of the particular combination turns out to be possible, or persuasive anecdotal indications about the particular combination turn up.

In any event, good luck as you proceed. Regards,
-- Al

Could you recommend a such a speaker?

My recommendation would be to try Tannoy, something like the Kensington, which, if you find on the used market, should be similar in price to used Cremonas, or maybe even less.

Although my Tannoy HPD 315's (12" Dual Concentric) are custom built, their drive characteristics probably aren't too different from the Kensingtons.

The point being, I am able use two quite different amps to successfully drive them in a fairly large room (16' X 34' W/cathedral ceiling). A very powerful VAC PA 35.35 push-pull EL 34 amp @35Wpc, and a SET 300B amp at 9Wpc.

Try to get out and audition some Tannoy speakers, and see what you think.

Could you recommend a such a speaker?

Some of the following may be significantly more expensive than the Cremona, and/or unlikely to be frequently available used, but fwiw most or all of the models offered by the following manufacturers would be suitable matches, and are generally well regarded:

Tannoy (as Dan recommended), Daedalus, Coincident, Audiokinesis, Audio Note, Devore, Zu Audio, Tonian, Horning.

It might also be worthwhile to search "MC275" in the Audiogon virtual systems section to see what speakers others are using with that amp.

Regards,
-- Al

Dear Al,

I just saw that their updated (and better looking) speaker, the Olympica III, has a lower sensitivity:
SENSITIVITY
90 dB SPL (2.83 V/1m). NOMINAL

IMPEDANCE
4 ohm.

SUGGESTED AMPLIFIER POWER OUTPUT
50W – 300W, without clipping.

Perhaps these would be a better match for my amp?