I love single-ended amplifiers but I've run into matching problems with lower efficient speakers. Even a homemade 15W SE (ultralinear in this case) amp with negative feedback couldn't drive a pair of current hungry Magnepan speakers to any reasonable level. But they did sound quite magical at low volume.
But the same amp on 91dB KEF speakers makes plenty of volume - in my friend's smaller living room.
So if you like head-banging levels or big dynamic music, then SE amps may not be the way to go, unless you run some "big powered" 805/845/211 amplifiers or get more efficient speakers.