This is a useful discussion for someone who is unhappy with their system's sound or who has been debating spending a boatload on cables.
'Tis an ancient debate and will never be settled in the court of critical listening although I think it gas in the court of science. For myself, I believe very strongly in both sides. ;^)
I use 12 g Auvio speaker wire. It's 50% bare copper and 50% silver coated. I haven't compared it with more expensive cable; but other's have measured its resistance against 10 other cables and it came in second to Canare 411.
http://www.whatsbestforum.com/showthread.php?14134-When-12-Gauge-Wire-is-not-12-Gauge!
I've compared it to 14 g and basic 12 g. Not a huge difference; but at 10 ft. length, I like the Auvio better. Tried bi-wiring. I Think I may gave heard a slight difference in non-blind comparison. I left the speakers bi-wired because it couldn't hurt.
ICs are a different story. I feel one MUST replace the generic RCA ICs that come with most components, but I've achieved a sound that I like without spending a boatload. I recently replaced a pair of 1 1/2 meter AQ AlphaSnakes with a pair of 1 meter WireWorld Luna 7s, their cheapest at $40, on my Oppo BDP-95. There was a change in tonality, the WW being a little brighter and seeming to have better detail. I like that; but there are some passages where it is too bright for me. I'll live with that because these cables accomplished something I could not, no matter how I positioned my Canton Ergo 1002DCs. Not only did they widen the already wide soundstage and provide more space between the musicians, they actually elevated the stage from the level of my navel to that of my ears. I was not expecting that! I had a friend listen, literally blindfolded, as I switched the ICs back and forth - or not. He heard the same thing and was able to pick out the WWs 4 of 5 times. The WireWorld cables have a unique physical design, which is why I chose them. Was that the cause of the difference, or is it just that they are 1/2 meter shorter? I don't know, but I'm planning on tying their Solstice or Oasis between my phono-pre and preamp. Maybe I'll keep them in the freezer for a week before I connect them. Nah. You can't believe everything you read. ;^)