Found some interesting info here Techdirt: $1 Million if You Can Prove $7250 Speaker Cables Are Any Better Than $80 Speaker Cables after thinking about this then checking it out on Google. I used to read What HiFi and in it they were always comparing cables and stating that you can hear the difference and i'm convinced that upgrading from the thin bell wire (shipped with my speakers) to specially made speaker cable made my set up sound better:S Might have been because there was a better connection or cleaner surface though:S
Point 35 is interesting, as are all the comments about it not making any difference whatsoever when using digital equipment as the only thing transmitting is 0's and 1's
But for analogue equipment, it seems that silver offers the lowest resistance of all metals, however seem most people probably wouldn't notice the difference anyway.
Basically, if you can't tell the difference between a flute and violin, then save your money
Edit: i'll also add that i'm kinda swaying the same way as tim in that maybe some dirt cheap speaker cable is the way to go, as spending 50 quid or more on cable might not sound any better than the cheap stuff, certainly not for a dj set up. Might be more cost effective upgrading the carts to some concordes instead or buying better speakers:S
Dunno for sure, but I bought some highly recommended (in What HIFI) and fairly expensive interconnects and didn't really notice any improvement in sound over the standard cables. Maybe my ears weren't good enough to notice the difference or the rest of my gear didn't make them shine:S