I have reached plateaus over the last fifty years where I had everything balanced as I wanted it… and, yes I just knew if I replaced one piece and it was going to throw everything off… and it happened. I always doubled the cost of a component, so it would improve the sound… but it would throw the tonal balance off.
Over time as I gained experience purchases would do what I expected… many hundreds of hours or reading, listening… experimenting. Over the last twenty years, my choices did exactly what I would expect.
I now have the system I have worked towards. So, no changes planned (My User ID). However, I have tweaks planned… shorten my speaker cables, podiums under speakers. There are always small things that make a system better at this level.