SET vs Class A vs tubes vs Class AB amps

All well-designed amplifiers (low output impedance, adequate slew rate and current delivery, low harmonic and IM distortion) operated below clipping will sound alike - Peter Walker of Quad fame.

I don't think that the class of an amp is universally descriptive of the entire genre, except for SET's which are so power limited that they require a whole different class of speaker.

I've heard Class A amps I liked, and some I didn't.

Best,
E

Horses for courses. 

I like my SEP lower powered amp, as it simply sounds far better than any other amp I've used in my current (or previous) system, possibly because Dennis Had knows how to design a brilliant amp that I can afford (I saved over 50 grand by not buying a Kondo Audio Note with similar output)...I'm evaluating a "Continuity sort of Class A" Schiit Aegir (also relatively low powered) that so far has shown some interesting tonal characteristics, and might earn a place in my amp collection...it has to pass a background test and be vetted by a committee before taking an oath...takes time. So far I still prefer my SEP, and yeah, you do get chained to a "different class" of speaker where high efficiency is paramount...my current main speakers are supposedly 99db efficient, but I've had good luck with a 90db or so pair as well...it's just nice to have more headroom from efficiency.