I certainly have, personally, experienced the improvement power cords can make on amplifiers...how about their value on other items, such as preamps with external powersuppies, and phono preamps....I know better than to apply layperson logic, which doesn't always work in audio, but it would seem that items that draw less "juice" would be less prone to changes in power cords....thoughts welcomed, but experience more interesting to me.....thanks
I am curious where people found fault with the video that Paul77e posted.  It seemed to me to be a reasoned argument, based on science, amplifier design, and hands on experience.

I am not an audio designer, electrician or physicist, but I did work in electrical manufacturing of power regulating equipment for some years, and I am hard pressed to imagine how a power cable upgrade could make a difference to sound, so long as it is capable of carrying sufficient current.  And even if you were pushing enough current through it to create resistance, isn't the worst result just a (very) slight voltage drop?

The whole thing about DIY cables using silver wire and hospital grade plugs seems silly.  Hospital grade plugs are simply more robust to handle greater physical force from pulling, and have a little more insulation to prevent contact shock.  And what possible difference could four feet of silver wire between the outlet and the component make when everything else from the generation source to the outlet is copper?  It's not as though the electricity magically starts at the wall.

If folks hear a difference, great.  That's all that really matters.  But honestly, how many who heard a difference did a real double blind test?

I would suggest that power quality is a much bigger issue for all electrical equipment, including audio.  Most PQ problems are voltage related, and most of those are sags.  Even a very short duration sag can mess with electrical equipment, especially digital switches and power supplies.  Installing a real voltage regulator (very expensive) or a UPS that puts out perfect sine wave power would be a good investment.

This is and will continue to be a never ending debate. You ask some good questions , all of which have been discussed ad nauseum ....my perspective is that , in the end, this hobby is about giving us pleasure inits pursuit and experience. We all, I think, have learned that measurements, science and logic have yet to explain all we perceive. There is no right and wrong , to me.  I have heard differences, but will never audition multiple cables.  I often use my experience and research to make choices. In the end I am happy, and that works for me....enjoy
Many of my cable experiments were done a little over tens years ago. I was most surprised to hear how power cords made the most difference on my CD player, followed by preamp, then amp (tube and SS). At the time, I had access to cables of many different designs and these experiments were eye-opening.
I find cables to have a quantitive effect, if you like the tone of the cable, a longer length will give you more of that tone, especially the warmer sounding ones.
@scar972 , there is logic to that, though we know that doesn’t always apply in audio.... source is critical, as well as their power supplies. Amps usually have robust power supplies, though a terrible cord can surely limit them. Source tend to have smaller supplies, as well as the fact that they are the beginning....
One question that I posed actually has not been answered in this thread, which is how would a power cord make a difference? I mean theoretically speaking. Would it not have to change the characteristic of electricity between the outlet itself and the component, and if so what characteristic is it changing? 
Running a cable the entire distance between the source and the recipient, such as from the CD player to a preamp, or an amplifier and speakers is one thing. But claiming that a small bit of cable tacked on the end of miles of a different cable can change-profoundly- electricity is something else.  What exactly is being changed?