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
Very nice so far! An actual adult conversation. I was starting to lose all hope that trying to discuss cables could only end up in the turlet.
Agree with proof of concept. Personally, I have found premium cables to provide blacker backgrounds and quieter quiet parts between the notes. Overall as improvement. But I also feel that there are economies of scale. I started out my power cord journey from stock cables to Shunyata Venoms. Then I upgraded to Deltas. I think that is going to be it for me. The incremental benefit of a further upgrade combined with my hearing, components and room make me feel like I have hit the sweet spot already. Ad in there my PS Audio power regenerators and dedicated 20amp lines from my breaker box and I am good. My systems are quiet, black with good resolution. I noticed the difference initially going from stock to Venoms. I feel that it is real. 
Following advice in this forum, I ventured into my first aftermarket cable being the Synergistic Research Master Coupler X2. There was a noticeable improvement, much the same as kingbarbuda describes that he perceived in his system.

I have just paid for a Grover Huffman Pharaoh power cable, and I'm waiting to take delivery. It comes with a trial and money back offer as well.
my experience with power cords has been ok. I bought the 12 + from Triode audio lab for my Conus Magnum integrated. This are not the top of the line. the difference was some what noticeable in terms of energy from voices and other instruments. just like if you gain a few more watts to your system. The issue I have with after markets inter connects and power cables is that they have an initial impression and when you get aclamaited to them you  don't notice or forget them. Don't get me wrong I still believe we should continue to strive for that perfect nirvana sound we all want. Its just that spending thousands of dollars in cables is not the way to go. its the pre amp, amp, cartridge speakers that has the most noticeable and lasting improvement to your ear. Just my 2 budget conscious 2 cents. but I agree experiment and let your ears make the  decision.