I reinstalled the game and lowered the res to 1600x900, dropped the water reflections and caustic and left the default physx values and it actually runs pretty well. Reflections and caustic while running at 1080p cut my FPS in half. Re: the values I had before are good for icicles, bullets and the sparks. I didn't notice much of an increase in visual quality with them at default. Water definitely needs to be higher than 200 though. There is so much water at 20,000. It's like a waterfall in a few places. lol I would leave the icicle count at 16 and particles at 300 as well as bullets and sparks with water up as high as you can. I am tempted to put all the settings down and run 1,000,000 water. lol I bet that would be awesome. I imagine there is a limit to the game engine at some point though. I haven't gotten to the water cannon yet but I imagine it won't work when the water count is below a certain number. It wouldn't work at 2000 either.
Have you looked to see if the AI can be adjusted? A lot of places in the game are really easy and I wanted to make it harder. Some of them won't chase you they just keep doing somersaults. lol
Crysis 2 is supposed to be out next year with their new engine: Cryengine 3. It will be for consoles too so hopefully it won't be cut down to the console level. At 1920 res Crysis really starts to slow down...1680 isn't too bad. 1 GT300 might be enough for it...I hope so anyway...but with AA it will slow it down a lot. Especially since it needs a 2GB card for high resolutions and AA.
The new batman demo arkham asylum has breakable objects, steam and cloth physx but no water yet at least. Here it is: