What may seem like a basic question is frequently controversial because your question makes a lot of sense, and so do many of the answers and opinions posted here. The simple answer is that it makes a difference. I use 2 power cords that cost $150 each, and heard definite improvements, mostly in background levels and bass weight, but I sure can see the point of being skeptical about all the hype and psuedo science as well. Let me relate this one experience that pertains directly to your question. A friend returned a favor by giving me 4 power cords to choose from for my main power source. I had no idea what they cost. All made differences, but not necessarily improvements, one stood out from the crowd and gave my system a touch of magic and soul, (if you will forgive the vagueness of such a statement) it turns out that the power cord I chose was worth around $1500. Being a gift, I was happy to be able to keep that PC for my $2200 receiver. Now if I was shopping for a PC I might look at power cords in the $100-300 price range for it. The difference the PC made was like a jump in class level for my system, and well, it should be at that price, but as Brucel pointed out in another post I also think that you get more bang for the buck by spending the higher percentage of budget on hardware (speakers, amps, sources, etc.). That said, some power cords may have some filtering capabilities that help clean up the AC from your wall a bit, so the fact that power may become distorted by traveling for miles is not the point, the point is that we can do something about it on our end.
