How or why power cords make a difference, I don't know, but they certainly can. I've listened to several "cable engineers" explain the phenomenon and I can't say that they all say anything that is consistent. Back when I had my own high-end shop, I experimented with power cables (as well as signal cables) quite a bit. Some made little difference, and some impacted the sound in a very audible way. I had my favorites at that time (about 12 years ago now) but the available offerings have expanded now. In particular I found that Cardas made some power cables that were reasonably priced (relatively speaking) that could "calm down" aggressive sounding amps, pre's and Digital gear. I also found that the Harmonic Tech Magic (???) cable was an excellent power cord. Twister Pair Designs also made a very affordable model that made both sonic and financial sense. I still find it pretty hard to drop much money on "upgrade" power cords, but I do have a few of em