They lost me for good after hooking up a $400 power cable to a $500 DAC and then stating that it measures, and therefore sounds, exactly the same as a $30 power cable hooked to the same DAC. Uh-huh.
huh indeed. You are telling me with straight face that a much more expensive audio product was shipped with poor AC cable as to need another one for $500??? If you paid thousands of dollars for it, what on earth did that money go to if it is not independence from mains interference or whatever the new cable supposed to do?
If there ever is a backward logic, it is that. That your expensive, boutique audio products are not engineered well enough that they need all sorts of tweaks. I would think it is an insult to their designers that you would want to mess with their products this way.
The products I use to test with these cables are state of the art despite their reasonable costs. And they show that if you buy a performant audio product, they are in need of no tweaks. This is demonstrated both with measurements and music null tests.