Much as I agree in principle, some streamers sound better than others despite the fact that all streamers do the same digital job and SOULD, according to the 1 and 0 theory, sound identical. Why a 10K streamer that operates entirely in the digital domain sounds better than one costing a tiny fraction bought on Amazon or Ebay sounds so much better, I don't know - but hopefully you can agree that the 10K one will sound better.
So, why a precious signal (even though it's still 1s and 0s) is adversely affected when subjected to a complex signal processor, I can't explain either, but I guess it has a similar explanation to the streamer difference described above.
I have never tried comparing a $10,000 streamer to a $100 one from eBay, but I have compared $10,000 CD transports to cheap CD transports back in the day. I never did hear a difference, or if there was one, it was so miniscule that I would not pay $10,000 for it. I agree that streamers are more complex than CD transports but I honestly can't see how they would make a difference if it enters my DAC, gets buffered, and then reclocked anyway. I know my DAC has a buffer because if you switch of the music, it keeps playing for about a second.
The practical (as opposed to theoretical) test though is simple. My Dirac Live is the version that cannot adjust any frequencies above 500 Hz. If I run Dirac and save the resultant filter, the top end (above 500 Hz) remains unaltered – in theory. My amp has a Subwoofer switch that directs bass only to the Sub outputs and "the rest" to the speaker binding posts. I don't use subs but I can select a crossover frequency between 40 and 200 Hz. If I set this for 200 Hz, nearly all the bass is absent from my speaker terminal outputs and only higher frequencies are sent to my speakers. I can now listen more closely to the top end without the distraction of the bass that will sound different with or without the Dirac filter. Are you following me so far? In theory the top end, as you describe should be identical, yet (with first class speakers) it is patently obvious that some of the top end sparkle / goosebump factor, call it what you will, is missing when I switch from No Filter to a Dirac Filter. All my visitors agree that it's not my imagination, but a real reduction in the feeling of excitement when a filter is engaged.
I know how your speakers work
I considered getting an Avantgarde myself, but then I heard the Acapella's and it was over. I have also heard maybe a dozen Avantgarde systems. I believe you when you recount your experience, but it is not the same as mine.
PS - I see you have rather similar speakers to my own Avantgarde Duos. Try this - switch off your subs and (as far as possible) eliminate the presence of bass to your Acapella High Violons. Then listen carefully to an exciting pience of music with and without a DSP filter that ADJUSTS only the bass. And for good measure change your costly (I guess) digital interconnects with nasty cheap ones. Will you hear any difference in top end sparkle? My guess is that you will.
I don't have costly digital interconnects. I only have "nasty cheap ones"
(Well, SOTM cables. They aren't too expensive).
PPS - I see from the diagram of your equipment setup that you crossover the signal and then bi-amp it. That's why your top end is not spoilt by DSP - it's not subjected to it! You have the system I described earlier where DSP can be used without spoiling the sparkle - by bi-amping and DSP'ing only the bass. Well done - but it would be spoilt if you used a single amp with built-in DSP for the entire speaker system.
I haven't updated my system thread in a while. I think my last post in there was in 2016? Right now it has been upgraded and the system topology is different. Now, the crossover is generated in the PC, 8 channels of digital is sent to the DAC, and from there to 4 amplifiers. All the passive crossovers in the speaker have been bypassed, and the amplifiers connect directly to the drivers.
In audio, you win some and you lose some. What I MAY have potentially lost in transparency by going with a digital crossover, I have gained back in spades by removing the passive crossover in the speakers. Not only that, I have linearized my drivers, time aligned them, fixed the room response, and I can design any target curve that I like. I can install VST's, and there are some very interesting VST's out there. For example, I use a "dynamic range expander" that looks at your audio signal and tries to increase dynamic range. There is another VST I use called a "declipper" that interpolates missing peaks that were destroyed by the loudness wars. I have yet another VST called MSED whose effect is to widen and deepen the soundstage. And my volume control is not like yours - it applies ISO226 equal loudness curves to the signal which gives you more bass and treble when the volume gets lower. And it does it progressively, not like the old "loudness buttons" that were either on or off. If I want to, I can perform all my processing in DSD with no conversion to PCM whatsoever. My next step would be to install BACCH crosstalk cancellation.
These are things which bring real tangible benefits which are easy to hear (and measure!) and the way they work is not mysterious or nebulous like say, a costly digital interconnect.
Neither do I subscribe to the objectivist mantra of "if it measures the same, it sounds the same". I am with Amir (the Amir on this forum, to be clear) that steady state measurements don't tell you the whole story. Which is why I use valve amps and strategically deploy good cable where I think I can hear a difference. I use Acrolink, and because it's so expensive it gets reserved for the midrange horn and tweeter. The subs and woofers have cheaper cabling.