I have a 770 and get 70-85 fps on ultra but I turn AA off. 680 should perform similar I would assume. Like most games at 1440p resolution, I see little point in turning AA on as it does little or no noticeable improvement and drops a lot of fps. My two cents - others might disagree.
Edit: Your card would be ideal for the Korean monitors. I like mine and managed to OC it to 120Hz but I have a defect so I'm in the middle of getting it exchanged. Even if you can only OC it to 75, it's still noticeable over 60Hz. I can't really see the difference past the 90's Hz range so I might back off on my replacement.
Edited by Xentar712 - 9/4/13 at 11:30am