Most effective tweak so far

[Kunter]

Based on my listening in the last couple of days, I am changing my opinion on this from "tweak" or "upgrade" to "absolute necessity" or even "you should be crazy not to do it"
I am really sorry for the time I lost listening to my system without dedicated mains.
Putting in a high grade power cable, instead of separate electric cabling, I think has the additional benefit of further noise reduction on the way. Ground, neutral and power lines all travel together that whole distance in proper geometry. And yes they are shielded against any interference from neighbour power or worse, data lines (I have tv and Ethernet cables traveling through the walls too).