I want to address, once again, the issue of whether power cords or interconnects or speaker cables or isolation components, etc. make a difference, but from a macro perspective. There is an article in the March issue of Stereophile magazine where the author mentions the concept of "auditory memory" as potentially one of the main reasons why people perceive music differently and why some people hear changes and why some people don't hear them. I thought it was an interesting notion because, generally speaking, some people have better memories than others, so it isn't hard to imagine that auditory memory may be analogous to ordinary memory. (Hmmm -- sounds like an interesting research project.)
Similarly, a question I have for Polkies is whether you hear music or feel it. I surmise that all of us do both, but to varying degrees, and it affects our ability to perceive changes in our system. For instance, when I make major changes in my system, I ask my wife whether it sounds better. Her response is always the same -- the system change either makes her "feel" the music more or it doesn't. She doesn't use terms like, "it has more detail," or "the bass is better." Rather, she talks about whether or not the music elicits a greater emotional response for her. On the other hand, I listen to changes in music quite differently. It's the classic left brain vs. right brain thing going on here.
There's a third group of people I refer to as the "brotherhood of the boombox." These guys don't hear system changes at all because most systems sound alike to them. To them, every amp sounds the same. They'll use science to argue that a power cord doesn't make any difference, but won't try it for themselves. They would fall under the category of "left-brained listener with low auditory memory."
Here's my hypothesis -- the extent to which people can perceive differences in power cords, interconnects, etc. is based primarily on their level of auditory memory due mainly to the degree to which one feels music or hears it. In short, memory and perception drive our listening experience. Thus, the self-proclaimed audiophile is likely to have a strong auditory memory based on either a "good ear" and/or a heightened sensability for feeling music. The abilities to remember and perceive music are pre-programmed or "hardwired" in us; however, one can "learn" to become a better music listener through repetition (it's the same way we commit things to memory).