Simply Q , so when my wife walks into the room and says wow,
that sounds better... What did you do to the stereo... without prompting...
That likely means I did something that to improve the sound.
There are many " real improvements" out there for your stereo system.
You can also change equipment and make it sound worse.
To say it is mostly in your head and not real, that is your opinion but I don't buy it. Just leave it at that.