I tried to prove what I was hearing could be measured, but couldn't.
I heard a demo of IsoAcoustics GAIA footers a couple years ago and was dumbfounded. It took me two years to try their returnable footers, which I did try in April of this year. I measured with the spikes that came with the 13A, then installed the GAIA footers, listened, heard a better soundstage, then measured and saw no meaningful difference that could be anything but run to run differences. So I thought I must be dreaming, so I reinstalled the spikes and the soundstage sounded like it did before with the spikes, measured again, no real difference, then reinstalled the GAIA footers, better soundstage again but isn't measurable.
So, there was a difference, which I enjoy, so I call that an improvement, but it's not something I know how to measure. So it must just be psychoacoustics at play. Whatever. If the GAIA footers provided no improvement, but also no degradation, I would keep them just for the looks and the ease of moving the speakers which allows me to test more without fear of damaging my floor. But since there's an "improvement" that I enjoy, that's just a nice bonus.
I'm of the opinion that so long as a power cord is correctly sized for the Current required by a device, then that's all that is needed. But, I actually do go further with it and decided to make all my power cords with 12AWG wire and plugs for anything that amplifies. All 7 circuits for my AV stuff are 20A, as are the receptacles, so I figure why not make the cords to the same spec?
Re OFC wire, it doesn't take much searching to find the industries that need OFC wiring and why, which is largely due to limiting chemical reactions and not due to electrical needs.