All this talk of placebo and expectation bias are just smoke and mirrors. It's quite possible to evaluate a change properly without bias or expectation if you set your mind to just listening to the music.

As to being ripped off, see here.

Sarcasm?
its only hifi Alan, no need mate.
We're all free to spend our hard earned as we please, sure thats right?

Charmin...
Who peed on your cornflakes?

Was a figure of speech.
Ah well, takes all sorts.

In this sort of discussion I can only speak for myself (as I hoped I made clear). I am most certainly subject to expectation bias, peer approval, induced dissatisfaction and all the rest, and that's despite having a background which has involved having dealings with advertising and PR people, not to mention an interest in psychology.

If I am just listening to the music then small differences pale into insignificance. If I am studying the sound to access if there is any difference then I become aware just how difficult it is to make comparisons of the moving target that is music. Even if listening to a short section of music there is so much going on that it is difficult to make a comparison - it is not as if you can compare two things side by side (as with two pictures) so much as one after the other and then aural memory has to be taken into account.

Given these difficulties I think it is well nigh impossible to come up with much more than a feeling about the effect of things. Not that that need be a problem as it is how we feel about a thing, involving all those pesky subconscious emotions, that most affects our ultimate enjoyment. If purchasing an item has a positive effect on our enjoyment in listening to music then that is a good thing no matter how it is achieved. After all listening to music in the home is an illusion. Last night I had Rostropovich playing Britten's First Cello Suite in front of me. With eyes closed the illusion was spookily realistic, despite there being fresh air between the speakers where the sound was coming from and Rostropovich being dead.

What interests me, and this not said to provoke, is how anyone can be so sure that they are actually hearing a difference rather than perceiving it. How is it possible to free oneself of the baggage that makes us human and our perceptions so personal. I think I could understand that someone very accomplished in mediation might have the skills to make a good stab at it; damned if I could though.

I'm certain I hear differences - when I do.
Sometimes subtle other times dramatic.

If I'm not sure I go back and forth once or twice.
If it involves spending money and I'm not sure I don't spend the money

It's the just listening to the music that is the real test. Small, sometimes tiny, differences penetrate the consciousness like no amount of concentration will reveal. That's why the best test is to relax and listen to familiar material. Sometimes it can take some time but your inner self will know for sure whether you hear a difference or no change.

I meant to quote this earlier, Malcolm. Not provoked at all, but I do truly believe that listening to music forms a deep emotional connection. We hear a lot more than the conscious listening reveals. I sometimes marvel at the small changes I perceive over the course of listening to an album.

You can't really lie to yourself and I am not inclined to try. I have rejected some components and some accessories that just didn't work for me. There was no expectation bias at work then, either!

Yes it's possible, but can be difficult unless one returns to the status quo after say a week of having listening to the change.  Many so-called improvements are just that: a "change", different but not an overall improvement.

Going back to check is the most vital part of the process!