I have tested 12 non-eccentrically engineered DACs level matched and blind from £1000 to &14,000 and I could not hear any difference of note, in as much as if there did seem to be a difference I could not repeatedly recognise it or tell one from the other, so I am content they all sound the same to me, or at least so close to the same to be inconsequential.
I can't speak for anybody else, obviously.
Having written that, I have also tested my hearing in my room at home and find if the music is playing 60dB quieter than my average level I can only
just hear it.
On that basis I do not find it credible that I would be able to hear distortion at a level of -60dB whilst music was actually playing since I can only just hear that level of sound when it is not playing. Since my listening level allows 20dB for peaks I also am content that if the SNR or SINAD is better than -80dB then it would be ridiculous to imagine I would be able to hear noise less than that.
So based on logical deduction (IMHO) anything with distortion better than -60dB and noise less than -80db would obviously sound the same to me here in my room.
There is almost no electronics available on the market which exceeds these limits so, for me, I am content that any difference I would hear in sighted tests non-level matched I will have imagined.
That is my logic for me tested on me by me