I agree that plain old 14g zip is fine.
I recently set up some new speakers. I bought some 16g zip at Radio Shack for temporary use until I received my order from Cobalt Cable (which I bought based on excellent reviews). The cheap 16g sounded fine.
The Cobalt stuff (for two mains, a center channel, and one of their "subwoofer cables") wasn't all that expensive ($250 for the whole set), but sounded no better than the 16g zip.