As far as I'm concerned, it's ALL about musical enjoyment. What the heck else is an audio system good for? You can't eat it, drive it or make love to it. (AFAIK. Please don't correct me if I'm wrong about any of those!)I've yet to hear a solid state amp whose reproduction bears even a passing resemblence to any instrument or any voice, but quite a few SETs that do. So the question is: Fidelity to what?
Good SET amps do not sound fat. I've heard quite a few that do, but remember, I said *good*. Not only good design, but equally important, good quality key parts, particularly iron and power supplies, but also caps, resistors and wire. The ones I listen to regularly sound extremely detailed and precise, without losing the organic sense the sand amps never have.
But, chac un a son gout, which, of course, is French for "to each his own goo."