I run BAT and McIntosh components and, to my ears, have never heard ANY difference while demoing PS Audio, Black Sand, Straightwire, Cardas, Parasound, Power Wedge and Jellyfish AC cords...
The audible difference will decrease as you improve the quality of power in your house and as your gear gets more stout power supply. BAT and Mac actually end to have robust PS.
On the same token, as you optimize the interface between 2 components, the audible difference among interconnects will diminish. Low source output impedance matched with benign input impedance and following capacitance of various kinds will do this trick.
Unfortunately, most of us simply don't live in the ideal world.
Let's also not forget various DIY options that can give you great sound quality. The "Asylum cord" is reportedly nice, especially for source components, and the VH cords have been around for a long time.
One can go quite exotic if one wishes.
The bottom cord is my DIY cord, which involves wrapping pure silver ribbon around a foamed-teflon copper coax, teflon-taping it all, then heatshrinking. The live and neutral legs are then "cross-connected" to lower inductance. The thing sounds fabulous, but it's so difficult and even dangerous(!) that I couldn't make another one even if Donald Trump wanted to pay me to do it...