.... I am quite skeptical that in a "perfectly" designed DBT with "perfect" immediate switching between amps that people could hear a difference. Same goes with the vast majority of speaker cables. ...
You should be so skeptical
David Rich and Peter Aczel, 'Topological Analysis of Consumer Audio Electronics: Another Approach to Show that Modern Audio Electronics are Acoustically Transparent,' 99 AES Convention, 1995, Print #4053.
Tom Nousaine, ' The Great Debate: Is Anyone Winning?' Proceedings of the AES, 8th International Conference, 1990.
Masters, Ian G. 'Audiolab Test: Six Power Amplifiers,' Audio Scene Canada, May 1977, pg 44-50.
Masters, Ian G. ' Audiolab Test: Amplifiers and Speaker Cables,' Audio Scene Canada, Jun 1981, pg 24-27.
Masters, Ian G. 'Do All Amplifiers Sound the Same?' Stereo Review, Jan 1987, pg 78-84
Carlstrom, D., Kruger, A., & Greenhill, L. ' Some Amplifiers Do Sound Different,' The Audio Amateur, 3/1982, pg 30, 31.
Smith, Thomas H., Peterson, Michael R., and Jackson, Peter O., "Are those Ears Really Golden?(Or only Iron Pyrites," The Audio Amateur, 1/80, pg 34, 36, 38, &32.
They all supports your skepticism
No need to post the cable stuff