I would not want to be forced to do a blind test.
I've spent to much on cables. Of all I've owned I like the Monster Sigma retro the best. I've tried a few expensive brands (will not mention the names). I've also heard cables that cost 6-7 times what the retros cost at retail. The guy who had me listen to these cables insisted they made a hugh difference. I heard nothing. If I had it to do over again I would probably stay away from the expensive cable game. It is amazing to me the claims made by people about cables. Keep in mind folks, many times people hear all this extra detail due to cables. This is after the very music they are listening to went through hundreds of feet of the cheapest cables available at the studio or concert venue. Cables that are being walked on and not properly cared for at all.
That being said, if you can truly afford it - go for it. My feelings about the cable game are the same as vman71. That is do they do anything at all. When I am being 100% honest, I honestly can't give you a definitive answer. I can tell you for the last 2 years when I need a cable I go directly to Frank at signal cable. I have not been disappointed yet. I also don't sit and wonder how much better my system would be if I spent $20,000.00 on cables. I've heard a system that had that kind of money tied up in the cables. All I could think while I was listening was this should sound better. I thought this because it did not sound any better than mine. We had the same amplifier and the same phono cartridge.