The crux of the matter will be if they are willing to submit their casual observations to the rigours of scientific methodology. I do not doubt that they genuinely believe that they hear the differences that they hear. The question is whether they can make this stick under controlled conditions. I once did submit myself to such a test, believing I would be able to distinguish between some quality but not exotic amplifiers. Just like everybody else, I could not. There have been many such tests, and they all produced the same result. It is a sobering thought, but also a cheerful one: good quality audio is affordable for many. Socially and culturally we can only rejoice in that.
The only expensive component is the speakers, and the reason is not hard to fathom: they operate on the interface between the electrical and the mechanical, and that is far more complex than designing a straight wire with gain. Just look at the measurements for distortion and frequency response and compare those with the same measurements for electronics.
Moreover, even good speakers have to play in imperfect rooms. So compare their response in an anechoic chamber or the open air, with their in room response, and you can see that you have your job cut out.
The only expensive component is the speakers, and the reason is not hard to fathom: they operate on the interface between the electrical and the mechanical, and that is far more complex than designing a straight wire with gain. Just look at the measurements for distortion and frequency response and compare those with the same measurements for electronics.
Moreover, even good speakers have to play in imperfect rooms. So compare their response in an anechoic chamber or the open air, with their in room response, and you can see that you have your job cut out.