Great topic. You have accurately described the problems which arise when trying to assess a new component. IMO the next step is to find ways to overcome the biases and desires of our mindset. Lets face it, when we spend $1, 2, 5, 8K on an upgrade we want a return on our investment. And if one isn't there, we can easily fool ourselves into believing it IS there. I've done it. And I suspect many others have done so as well.
But you and others have given the answer to the problem. @spenav has described my (and others) method saying,
It takes me months to assess a new piece of hardware and I usually won’t know until I remove it and see if I missed it.
This seems to be the method of you and most every poster so far. I don't take months to assess an item as others have said, but weeks for me. And like spenav,
I usually won’t know until I remove it and see if I missed it.
That, for me, is the key. I believe it is easier to see or hear what we've missed than to hear what was gained, though that is in a mental database for comparison