AMD isn't an option for processors. They don't have the ability to properly supply Apple, and their laptop processors aren't as energy efficient (read: poor battery life). The chipsets and graphics are indeed an option, as both are fairly solid over all. The IO for AMD's chipsets are currently 5-10% less than Intel, but that is less of an issue for laptops. Nvidia and AMD each have their strengths in terms of graphics, and both have been utilized successfully by Apple. If Nvidia wants to pick a fight with Intel however, they could lose quite a bit in the end.