I just bought myself an Alienware M18x last week and immediately installed Crysis 3 to see how its Nvidia 680M SLI performs is like on this gaming laptop. Installation went fine but I was able to max out all the graphics under Crysis’ settings.
The game is choppy and stutters at 30 FPS with vsync on. If I turn the Vsync off in my Alienware, it lags even more (which is obvious). I had to do some tinkering here and there to overclock the GPU and after clocking the 680M GPU to 1000MHz, I was finally able to play at 60 FPS. Alienware M18x Aero Patch
Use the settings shown in the aforementioned screenshot to achieve 60FPS.