@ace17 Good post. It has to be opinions, because we can't prove it. Even if we could prove it why would we bother just to satisfy someone else? But the deniers can't prove it doesn't make any difference either. They try by stating something like "copper is copper, the only difference is the gauge" but that is not a complete argument, therefore it means nothing, and we know better.
If audio forums had no opinions they would not exist.
I don't know if it like reverse confirmation bias, but I am much more likely to get buyer's remorse than expectation bias, and therefore (maybe) do not hear improvements as easily as others may. And not just with audio, but everything in life. It is not very often I add a new component or make an adjustment and say "oh wow, that is so much better" It is when I go backwards is when I notice the difference most- I listen for a while with a new product (after break-in) and think not much of a difference, but when removed or going back to the original setting or setup is when I say "oh wow, that is worse". Perhaps many do their evaluations similarly.
Perhaps with an interest in psychology you have some curiousity in this as well: I still wonder why they (the deniers) are here, like what is the point of going to threads on audio forums, search for cable reviews/experiences, and then question someones findings? Do they just like to argue? Enjoy conflict? Or are they trying to "save us"? I don't think they really care about our financial situation.