Interesting thread. Here's my take, and I apologise if this has already been said better by someone else.
Music is a puzzle. I have no idea why humans can get so much emotional pleasure from listening to it. But we do. We don't all get the same pleasure from the same music, however, so there is inevitably an enormous subjective element in the enjoyment of music which makes analysing the pleasure we get from it even harder.
When it comes to the hardware we use to replay recorded music, pursuit of objective fidelity is desirable, and not to be scoffed at. However, the concept of fidelity has an irreducibly subjective component, because we're trying to create a emotional response. What works for me might not work for you, etc. This means there is huge scope for snake oil purveyors, because we can and do fool ourselves. The placebo effect is real. Vigilance against irresponsible foo is necessary and desirable, then, but there are bound to be areas where it's really hard to say what's foo and what isn't. (There have been several occasions over the years when I've 'upgraded' through several steps and convinced myself that my system's never sounded better, only to swop back to a much older system configuration for some unforeseen reason, to discover that the old system didn't in fact suck, as I'd expected, but actually gave more pleasure than the new one.) To sum up, neither unqualified objectivism nor unqualified subjectivism can be allow to stand. We all just have to muddle through, hoping to enjoy what we hear and trying not to be ripped off in the process. The message I take from all this is that a little humility is essential in any attempt to discuss what we hear.
We also need to remember that listening to recorded music involves the imagination - we hear sounds emitted by an audio system, and we imagine we are hearing people singing, instruments playing etc. If all goes well, we get the emotional pleasure we sought.
What this implies, of course, is that people who can enjoy music fully via lo-fi reproduction have superior ability to recreate a musical experience imaginatively to those who enjoy music most via hi-fi. I therefore regard my own hi-fi habit as sign of a kind of musical disability, and I try to remember this any time I post on a hi-fi forum.