... abit confused: how does a power cord affect the presentation of sound...

I repeat: if a PC is supplying enough juice to a component (sufficient awg and OK metallurgy), then if you hear a difference it must be because of one or both of two reasons: the PC is doing something to the current flowing through it, and/or the PC is protecting the current from some sort of contamination from outside.  What other options are there?

For instance, Wireworld says their PCs block (outside) interference and absorb (inside) tribolectric noise.

This is just beyond me. Nothing matters but the power cord from the receptacle to the component? The panel box, wire in the wall, transformer in the component that isolates the primary from the secondary, filtering in the component none of this makes a tinker's damn only this freaking 4 foot power cord?? Jesus Christ people learn how electricity works

Don't fall for the red herring of "all that romex and junk" the power goes through before you get it. All that came before it is moot since what you need to do is get the best you can from where it all terminates: the outlet.

That was assuming that everything is to up to snuff and to built to code.
Of course, you can put in a better panel box, better grade romex, etc. but how many have the funds to go that far? The OP just asked about PCs in a normal setting, not how it figures into the universe