I think it was Einstein that said “Everything that can be counted doesn’t necessarily count. Everything that counts cannot necessarily be counted.”
There are so many variables in our stereo systems it's hard to know which of them matter and which are just there to drive us nuts.
For example, every electronic piece we own radiates unwanted high frequency energy. Some radiate a lot, some only a little. What we can count on is that any product that passes CE certification is at or below a certain level. What we cannot easily know is how important that particular level is to our sound system. We suppose it matters, but the question comes down to how much?
If we thought it was super important (and plenty of folks do) then we would roll up our sleeves and paper the insides of our equipment with EMI blocking materials. (oh the stories I could tell about this). But most of us don't because while it "counts" there's a practical side to all this madness.
And it is to the practical side I want to focus on today. The question of what counts really comes down to a matter of practicality. Where to put what energy into making things better.
Some focus on vibration control by spending thousands on footers and platforms while others ignore it entirely. Then there are fuses. And cables. And power. And so on.
So where to turn to? My vote is sticking with the mainstream. The obvious, like power, interconnecting cables, and the quality of the equipment itself. In other words, the most common and accepted points in the system that are universally accepted.
Everything counts. The question always remains, by how much.