Regarding the discussion pertaining to the value of trained listening in the evaluation of audio equipment, much now foundational research has been published on this topic, especially by the honored and well-known audio engineers Floyd Toole and Sean Olive. Here is a great summary article by Sean Olive that appears on his blog:
Toole and Olive are both retired now from their research careers at the laboratories of Canada's National Research Council and Harman International.
FYI, Toole has a forthcoming fourth edition of his seminal work, Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers, Rooms, and Headphones, that will be published in October. It will include contributions by Olive and other distinguished researchers.
Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers,