Hook up your system to at any point in those 100s of miles of transmission, at step up transformers, step down transformers, at 25 yr old 6 GA and 12 GA wiring, and your system will sound different at all the points you choose. One can't argue that.
What matters is how it sounds at the outlet where utilities code tells you it has to perform within tolerances there or it's not right. AFAIK the same code at the outlet doesn't apply to any point along those 100s of miles of transmission. Enough of that red herring argument. It's been shot down so long ago. How it keeps on like a zombie is beyond me.
The same goes for power supplies in amps and sources. Some just make them good enough so as to not burn down your house and some can occupy the whole underside of some gear or require its own chassis. When made like the latter, I can see how different PCs would have little to no effect, but the majority of components aren't made that way.
I've only heard slight differences but enough of one to choose one way over the other. Having heard the better way, how could one settle for less for not much more outlay?
All the best,
Nonoise