Pretty much any speaker will PLAY with lower power, but also most good speakers, even "efficient" ones, will sound better with more power (this has nothing to do with the accuracy of the reproduction chain, of course; "loud" does not mean "accurate", obviously..
Anyway, Maggies will play OK with low power, but if you want the MOST out of them, more is better,and there is no thing such as "too much" unless you have an amp that misbehaves. I would guess that is true with any "inefficient" speaker.
Match your hardware to your speakers. Low "watt" tube amps/integrated will drive your "efficient" speakers nicely, I am sure. ARC makes a couple, as do others, I am sure.
Cheers!