I have yet to see a reputable report that says the high-dollar speaker cable makes a hill-of-beans worth of difference.
An interesting article on the web (with sources cited):
http://home.earthlink.net/~rogerr7/wire.htm
Another interesting site on the web (suggesting all sorts of things including relating speaker cable to the Greeks and the great pyramids):
http://www.fsaudioweb.com/listen/cardas.html