How far have ss amps really come in the last twenty years?

Teo, it's an appeal to authority because it isn't backed up with any evidence or answer, merely assertion about talent/credentials.  Your response reduces to an irrelevant and incomplete assertion of what ears do (even if we stipulated that, it wouldn't necessarily bear on audibility of differences), and then has several paragraphs that can be summed up as "I'm awesome, you're an idiot, get off my lawn".

• I remain open to the possibility that I am an audio philistine, but I have my doubts given my long and continued experience with live music, the reference standard
  
• I have admitted I sometimes hear differences between amps, but, after reviewing evidence (incomplete?)  I am also open to the possibility those were explainable by power/obvious artifacts or simply not objectively audible
• I have explicitly asked for further evidence that I may have missed and shown people what I have reviewed.
• I've freely admitted I enjoy the hobby no matter which way my beliefs go on these subjects, and, after all, I don't listen blind. 
  
• But who wouldn't want to know?
  

Your response to this is "you're an ignoramus, get out of the hobby".  This attitude closes, rather than opens, minds.  Furthermore, it is suspicious.  I've come to understand from my 31 years of business experience that nasty bluster is most often a smokescreen.

“I’ve come to understand from my 31 years of business experience that nasty bluster is most often a smokescreen.”

>>>>>Appeal to Authority alert 🚨

@geoffkait - I view it as more of a probabilistic inference, but I'll happily grant your point if it helps turn the dialogue in a more productive direction.

I have admitted I sometimes hear differences between amps, but, after reviewing evidence (incomplete?) I am also open to the possibility those were explainable by power/obvious artifacts or simply not objectively audible

What is 'objectively audible'??

Hearing amplifier differences to an educated ear is no different, than, to an experienced race car driver feeling a bit of difference on the accelerator pedal with a new small tweak done to the engine, which I have witnessed, living near Daytona. Or, my best friend, a guitarist, picking up 20 similar guitars by the same manufacturer, and stating one is preferable to him, by sound and feel. Or maybe, a certified wine sommelier who does tasting for a manufacturer before they decide to bottle it. I understand the doubt people have, but, does it really matter to continue the argument ? The reality is, if we all, the audiophile community, heard no differences, wouldn’t the high priced gear go bye bye, or, just 1 or 2 manufacturers would be left for all of us ? I say, let those folks, such as ahofer, be, and let us all just enjoy the realities of our hobby. It is getting tired, all of the naysayers and " trolls " ( yes, I needed to use the term ), telling us, it is in our minds, or, we are lunatics, or whatever. I have been trying to ignore these folks, but as always, sucked right back in to the arguments and discussions. Just some thoughts. Enjoy ! MrD.