I'll add my two cents to this story. I was very skeptical over the effect a power cord could have on my equipment (Ayre) but I ordered three aftermarket cords just to see. I put all in at once. The system sounded worse (one dimensional). I was astounded that it could have any effect on the sound, but it was clearly worse. I repeated the experiment the next day with my wife and we both thought we heard a difference and it was worse. So I packed up the power cords and sent them back. Then I faced the dilemma- do I go on an endless quest to see which if any of the many power cords on the market would make my stereo (pre, amp and disc player) sound better or do I just leave well enough alone and go back to listening to music. I chose the latter and am happier for it.
Do power cords make an audible difference?
I recently discovered the inexpensive Pangea AC-9 power cord. It was so inexpensive I decided, just for kicks, to buy one for my sacd player and my integrated amp. I was extremely doubtful I would hear any difference at all. I plugged them in, turned on the system and I was surprised. I immediately invited a non-audiophile over for a listen. She had only heard my system for maybe 30 minutes with the old cords and I asked her if she could hear a difference. After listening to only two tracks she said "it sounds more clear". This is exactly what I had thought. I also noticed the sound stage seemed bigger. Now, it's not A huge difference but it is noticeable to the casual observer, so it is significant, which is more than I hoped for.