This discussion has been going on for a long time. Power cables are not going to fix anything. Speaker cables, I have my doubts. I use the cheap stuff, but would go for all copper if I were splurging. On the other hand, I have bought about-dollar-store-cheap interconnects with problems, so I go for the fancy Amazon Basics level stuff myself. I get the guys that buy aesthetically pleasing cables, but that's a different story. Here's Bob Pease on the subject(s):
https://www.pearl-hifi.com/06_Lit_Archive/02_PEARL_Arch/Vol_...
> Unlike conventional power cables, which have propagation speeds that are less than 50% the speed of light, the Valhalla 2 Reference Power Cord has a speed of 91% the speed of light.
Thank God somebody is making these. Imagine if we had to wait almost twice as long!
Also, from the manufacturer's brochure: Unlike conventional power cables, which have propagation speeds that are less than 50% the speed of light, the Valhalla 2 Reference Power Cord has a speed of 91% the speed of light.
[1] https://audiofi.ca/products/valhalla-2-power-cord?variant=34...
EDIT: On a more serious note, check out https://www.audiosciencereview.com/forum/index.php for real testing, where the dollar store speaker cable performed (surprise!) as well as the fancy cables. The fancy cable company was not happy.