Your
copper vs. silver example verges on a strawman argument. Yes, of course, audiophile make ludacris claims sound differences -- speaker cable lifters, AC cords, silver USB cables, green markers for CD edges, 'Brilliant Pebbles', and on and on.
I gave up on that sort of rubbish many year since. I once did some sighted listening to different interconnects; at the time, (12-13 years ago), I thought I hear differences. But I very soon realized that the differences -- such as there might have been -- were minute and, further, that I would have no chance of pick which was which in a blind ABX test.
But amplification is another matter and the topic hear is op amps. We know op amps measure different so it isn't absurd to suspect sonic differences. Amir has measured op amp difference, e.g. his review of VTV Purifi amps with SIL 994EnH and Weiss OP2-BA -- differences but too small to hear?
Humm: just maybe.
(Parenthetically, I think one is much less likely to have difference between DAC filter settings than op amps,
but hey, I have no proof one way or the other.)
I'll confess that I am not convinced that the standard, blind ABX testing can reveal the all differences that experienced listeners can hear in real-life music listening. Constantly citing the ABX canon doesn't definitively prove "no audibled differences" it to me.