Crysis running at 2560x1600 on very high
http://img258.imageshack.us/img258/5006/29378126jl1.jpg
http://img232.imageshack.us/img232/7215/36487937lt4.jpg
http://img258.imageshack.us/img258/9109/24253128fx8.jpg
What did I do?
Read this http://www.tweakguides.com/Crysis_13.html
Put everything on high, then add the "very high on the cheap" commands to System.cfg or autoexec.cfg (either one needs to be created in C:\Program Files\Electronic Arts\Crytek\Crysis\Game\Config) or even in the target line of your shortcut. Select your native resolution, leave AA turned off (oooooobviously, FSAA kills anything in it's path)
You do not need SLI to run this smoothly. I do because of my behemoth resolution, but 1920x1200 should run just fine on a GTX or Ultra. 1680x1050 should be fine with a GT, and anything below its a walk in the park.
This is the best way to run Crysis folks. Hope you enjoy.