I bought my first aftermarket power cords after getting a PS Audio power plant, the Stellar PP3. First, the cord the PP came with is pretty darn stout. I replaced it with AQ’s NRG4. I got two Shunyata Venom 14s for my Rogue Sphinx amp and DirectStream DAC (Magnepan .7 speakers). I have moved them around and don’t hear much difference between cables, but overall the system has what I’m going to call greater articulation. It’s just clearer sound. I’ve never used the $$$ cables so can’t say. But I suspect the “diminishing return” curve kicks in really, really early once a good conductor, insulator and connector are used. But I guess that depends on your definition of good.