Upgrading power cord.. proven upgrade? or crap?

Its all CRAP. Sound.au.com has some facts on the situation if your interested in those (under the articles section) Read it for yourself, its your money. The only thing is is that there are people who will lie to you to take your money (and have little sheep following them). Be wary of analogies, scientific anecdotes, and then flat out lies. Analogies can be useful in illustrating a point, but please bear in mind they are not the same thing; however, in audio people like to use them to decieve. For example electrons and water both flow in what we call current, but when it comes to what they flow through they behave differently. Water running through a sewer that then tapers down to a 1/2" pipe will never really flow much beyond what the 1/2" pipe will allow (You know this intuitively; pressure can change things some though). However, 10' of 10g wire that tapers to a 2" long 18g section will not suffer the same effects--its the total resistance of the wire that counts. So the 18g section will impede the flow of electrons somewhat, but not in the same manner that the water through a smaller pipe will. Just trying to give you some sort of an example of the crap you'll get. Scientific anecdotes are just a sprinkle of this and that without a consistent organized arguement/explanation. And lastly some will lie. Some will even admit that the operation behind there product is a hypothesis--i.e. it never even entered the testing phase to determine its validity or existence (because they can't). The microdiodes theory caused by oxidation on the surface of the individual strands of wire within a cable is just one such example (no one has measured its effects; after 20 years!). And microphony, induced by vibrations causing the individual strands of wire in a cable to "move along" one another, is real, but its so far below the noise floor of even the best amps you'll never hear it. All in all, you can get better gains with your money elsewhere.