I'm late to this thread but my experience is the most dramatic effect was when I replaced the stock cord on my phono pre (EAR 834) with Nordost Blue Heaven. I tried the cord on my int. Amp with no discernable sound improvement.
Power cord replacement suggestions
If i were to delve into the fanatic behavior of replacing power cords, is there some concensus on where the most impact would be gained, whether on source, pre, or amp, or is it just different for every system and need to experiment. Thanks for any advice.