The link didn't work for me, John, but I found it from the Super Powerkord page. While too late to reply using your criteria, it seems axiomatic to me that different cables will perform differently. Whether they are audibly different, and if they are whether it is an improvement, is another matter. But they are different!
i note that one reply above mentions several Chord products. I have attended one of their demos where they use about five different sets of cables. No-one present would say there were no difference. I didn't universally prefer the better ones but the best were noticeably superior. Naturally it wasn't blind and I suppose the presenter may have influenced us, but I would be surprised.
I am definitely a believer, and agree with the OP that it seems foolish not to use something decent for a good system. I cannot imagine that everyone who has ever upgraded a cable is deluding themselves.