I’m not as savvy as some here about electricity (such as atdavid) but a few things. One, a reviewer once suggested that you can often improve by defeating the ground of any power cord. In other words, use one of those cheater plugs or yank out the ground prong. It works, I can testify I’ve compared many times with different components -- and in different houses -- and the ground is usually dirty. Maybe there are other ways to "clean it up" but I don’t know. (Although yes, you are taking a chance with shocks, but so far I’ve never gotten one)
The other thing is a question -- how can a power cord even constructed of pure copper or whatever, improve your sound when all the wiring in your wall is just ’average copper’? I know the cords can improve, I just don’t get how that could work. It makes some sense to me if you start with a power regenerator such as a PS Audio