I had to join to post this but so many of these replies are WRONG it just really bothered me.
An 8800GT and Q6600, even if they are both at stock speed, CAN AND WILL run Crysis at 1920x1200 completely fine as long as you tweak a couple settings. Most of the performance drop when using higher settings comes from a few obscure variables that you can safely reset to lower values without effecting the image quality in a noticable way. Unfortunately I have Crysis on my dads computer (which is Q6600/8800GT/1920x1200/Vista 64 Ultimate) and not this one so I can't pull up the specific settings I changed but there are PLENTY of tweak guides (such as
http://www.tweakguides.com/Crysis_1.html or
http://www.incrysis.com/forums/viewtopic.php?id=11614) that explain with great detail what you can change and what effect it will have. There are some pretty simple ways to make it look really good though.
1: Using a 64bit OS run the 64bit launcher for the game. The performance increase is significant over running the 32bit launcher or playing on a 32bit OS.
2: Force DX9 mode if in Vista. This is a huge increase in performance and you can re-enable most of the disabled "very high" settings for virtually identical image quality without the performance hit.
3: It is ABSOLUTELY VITAL vital to change the texture LOD settings for the terrain as well as the parallax occlusion settings. These changes will increase the visual quality of your game to far beyond what very high will give you, and for about 2fps drop at that. Scroll to the texture and LOD section in the 2nd link above to see some comparison shots. Once you use these changes you will never be able to play the game without them.
4: I recommend using the Natural Mod and also the FFT water algorithm mod/change (google these). The Natural Mod changes some lighting effects to give the game a more realistic look and the water mod uses the FFT algorithm to give Crysis very realistic waves.
Combine these changes with a few other tweaks from the above guides or any of the other guides and you will be playing Crysis at 1920x1200 using high/very high settings. I know this for a fact because that's how I played it. An 8800GTS 512MB would perform a little better or allow a few extra shader operations but one of the main limitations is that 512mb ram at this resolution won't allow you to max out the texture resolution. You can still get it pretty high though and in combination with all the tweaks you will end up with good performance and an image quality that is SUPERIOR to the default very high settings.