I did a kind of A/B test over several months between one of those audiophile Class-D amps that were the rage so many years ago and a simple single-ended tube amp that I had built from schematics.
Both sounded good to my ears when fired up. They were, for me, indistinguishable in sound quality.
However a funny thing happened after listening to the Class-D for weeks and then plugging the music source into the tube amp and firing it up: some indescribable "listening fatigue" just let go and was nowhere to be found with the tube output.
Like I say, I can't even put my finger on it, quantify it, but there was something just more calming about the sound reproduced by the tube amp.
Sure, not a blind test. And I have noted in the past a kind of bias I can have toward something I made myself (ha ha). But perhaps when the audiophiles start into some long diatribe about "even vs odd harmonics" there may be some subtle psychological effects they're poking around.
Regardless, I was sold from that point on. All my music listening around the house comes through my home-built tube amps and I am a happy listener.