Why worry about AA with Crysis? Just turn it off. I can't tell the difference between 2xAA and 8xAA, at least not to the point where the performance trade-off is worth it. If you had a card that could do 200FPS in Crysis at Very High, sure, turn on AA, but we don't have that. The performance hit isn't worth it.
Also, with AA off, you instead get EdgeAA, which isn't really AA and has a slight blur, but it also smooths the foliage, which AA does not. So, it's a trade-off. Even without AA, you still sort of get it, and then some.
If you really need AA, stick to 2x, but it's a travesty to use "just" High on a GeForce GTX 560 Ti. I play at Very High AND have alot of stuff raised even further with CVars. There's no way I'd trade that for some AA that does a bit better on the gun than the EdgeAA already does (which you'll never notice when moving), and lose the foliage AA atop that (some do prefer the sharper look but I can't stand the pixels/jaggies with the leaves).