Whatever changes we affect in our systems have repercussions: a new preamp changes the synergy of what came before it, records sound different with a new phono cartridge, AC power through a regenerator is radically different than straight from the wall.
Our systems are sensitive enough that we need to be mindful of the repercussions of change. Even setup changes have their repercussions.
The trick with repercussions is to give them their due. Too often I have found people expecting isolated change when performing an equipment swap.
The idea that more than what we directly change has a broader impact on sound is a good reminder—something to tuck away for future reference.
Our systems don't exist in a vacuum.
It's better to imagine them as parts in a chain. Each link affects the other.