"On SET amps the key here is not just Caps, resistors and etc but the trannies are the keys elements which will make the amps sound best. "
Not on SET amps - on all music reproducing or generating equipment. Thats like saying "The key on binoculars is having a good lens!", as if cameras, microscopes, etc don’t need that either.
The second most important thing to keep in mind is don’t let anyone say to you, "I doubt this change will matter because of X Y Z position or capacitance etc". They dont know what you have to begin with, and the part may be so cheap it causes a lot of damage to the audio because of its physical nature. Replacing it with audio-grade may make a world of difference, no matter where in the circuit it is. A Leica lens may have 20 glass elements which serve a different purpose in the schematic, but if glass #14 or #4 is made out of ikea plastic, replacing it will naturally cause a huge improvement.
Recently I had my eyeglass lens replaced with a very high grade material for 2x the cost, and while the Rx was still slightly off, the overall experience of contrast, detail, color, distortion, was far superior. The optometrist thinks only in terms of his narrow view of measurements, getting the focus to land correctly, which is important. But won't usually talk to about the myriad of esoteric enhancements a better material brings, even with the wrong Rx. Audio in electronics is similar, hence why many systems dont measure well or are accurate, but present special qualities of music.