Our guide for quality does have a baseline in audio - fidelity. For example, if we knew for certain that we owned a power amp that was ideally faithful in reproducing the audio signal into a speaker without distortion or coloration, then we would be listening to the highest quality component we could ask for.
The reality is that power amps are not ideal, they distort into a complex load, like a loudspeaker, in various degrees. The 'tube sound' for instance is, like I have stated many times before, is the tendency for the amp to resist changes in output impedance due to complex resistance changes in the speaker. Pure SS amps struggle with this, and can clip quite easily. Tube amps struggle with high output impedance, thus causing microphonic effects and speaker cone ringing.
There's a lot to know about audio. There's a lot of science, experiments and engineering lessons that we all have access to. What I don't like to see is people sticking to their own way of thinking simply because it's what they are used to thinking about, then offering up a cop-out like 'we all have our own opinion' or 'everyone hears differently'. While those are true to some extent, that shouldn't be the end of the discussion. How can you ever know for certain your way of thinking is infallible? Isn't it reasonable to support your views with objective, verifiable measurements and formulas? We should strive for knowledge with the resource of this forum, not simply yak to each other how we think audio should be. Because really, if there's no sure way to arrive at quality, and fidelity, and therefore ultimate carefree gear, then we're just wasting time talking about it all.
"It should sound like it isn't there" - BillD
When you no longer think about your components when you listen to music, you have arrived.