Are future improvements in Amp/PreAmps slowing to a crawl?

I did a comparison between the Audio Research DS450 and the GS150 at a local shop recently.  GS Pre frontend and VPI turntable via Vandersteen speakers.  Nice setup.  The sound thru the DS450 ($9k), a switching amp wasn't too bad, but, wasn't what I'd call wonderful.  Then the dealer switched over to the GS150 ($20k), yeah, MUCH better.  In fact I brought my daughter along with me and she told the salesman flat out "the 1st amp was Broken..."
Now, one would expect a $20k amp to sound better than a $9k amp.  And, tubes do sound different than SS.  But, at $9k the switcher produced "sound" no magic, no music really.  So, yeah switching amps have a long, long way to go.  The GS150 tube amp, not really sure it could get much better, nor do I feel it would Need to.  Hey, maybe in 50 years switching amps will be as good as modern tube amps are today :) 

Was the ouput level matched to within 0.2 dB?

I can hear a tube from way down the hall. So can the guy under the bridge. No mystery there. 🕵🏻

Mr. Paul.  I have an ancient Sony strd1011s in the closet that kind of does what you suggest a perfect amp does.  There's a bunch of goofy low-fi surround/reverb effects that allows one to approximate what different seating positions and distances in various venues would sound like.  That thing is cool to play around with, but it is far from perfect.

I might agree that a "perfect" amp would sound like no amp, but I completely disagree that a "perfect" amp would allow a volume knob to function as a zoom for proximity.  That wouldn't be "perfect" to me, except perhaps from a point source in a true anechoic chamber.  Cues for distance include much more than just volume.  If the amp included those cues, it would no longer sound like "no amplifier." 

@roger_paul 
If you're going to come here and tell me you've built the perfect amp I'm going to call you a liar. You have not. I've asked for a concise definition of it's operating theory and measurements and you've talked in circles. 
Your understanding of a volume knob's function doesn't even make sense. If a flute is miked 15 feet away and recorded, the reproduction system should present that flute 15 feet behind the speaker. If you turn the volume to a whisper it stays at 15 feet. It crank the volume to 11, it gets louder, but stays at 15 feet. This truth is obvious to anyone who's heard a decent stereo. The spacial distance information is in the recording. Adjusting volume is nothing like moving around an auditorium. If you go wandering around a venue you're not just hearing the reduced magnitude of the sound. You're hearing the acoustic character of the room and space between you and the instrument at the various points in the room. Your explanation makes no sense.