I'll be honest with you. I haven't tested any luxury cables. For RCA cables, I've got Radio Shack, Monoprice, Stinger, Kabel Direkt, Monster, and probably a dozen other unbranded cheapos; and not one set of them affects the frequency response of my speakers in the slightest. They still sound like MB Quarts -- which is to say, astounding.
For speaker cables, I'm just using Amazon Basics CCA. I generally recommend Monoprice OFC to others; but since my speakers are only about 6 feet from my receiver I haven't bothered to replace it. (For reference, CCA is about 2/3 as efficient as OFC.
This page describes the appropriate gauge of OFC to use for a particular distance.)
For HDMI, my cheap Chinese crap cables have caused exactly 0 artifacts or timing sync losses.
This page demonstrates what happens when the quality of HDMI cable doesn't meet the demand.
Optical cables are the same -- as long as they don't disintegrate, I'm happy.
For power cables, since I have no influence over the quality of power from the electric company substation to my wall outlet, I have no reason to believe an exotic cable the last 5 feet of the way would make the slightest difference to anything but my wallet.