So I've been looking into some specifics of the suspected graphics cards in the updated iMacs...whenever and if ever they come. I was surprised to find that the GTX 680M (the frontrunner for the top end card in the update) is only marginally better, at least according to this site, than the Radeon HD 6970M, the top card in the current iMacs. Has there been some kind of mistake, or what's the story here? I was under the impression that it was like a 100% increase. The site I got the screenshot from.