While I won't admit that the 2160 is a 'joke' of a processor, I know for damn sure it isn't the greatest. That aside, you need to overclock it some more, whiteshark. while 2.2 is faster than the 1.8 it came at, it's ONLY 400mhz, which might get an average of 1-2 more fps***. Even using the stock cooler, you should easily get that red-headed step child to 2.7-2.8, and 3.0 is feasible with little or no addition to vcore. Overall, you might pick up 3-5 fps from running it at stock speeds, but it's something.
Beyond that, you need to whip that 8600GT until it's giving you 110%. Overclock that too, mine would run 650 on the core without artifacting any games, but I could do 690 in ATITool. If you feel up to flashing it's BIOS with some more voltage, you could probably break 700 pretty easily. Your vmem is already running what mine did, but I'm sure you can push a little out of it too.
Overclocking both of these isn't going to let you play crysis on high settings by any means, but you should pick up a handful of frames I'd guess. If you still decide you need to upgrade something, I'd highly suggest it be your video card. 8800GT 512's are getting cheap, and the HD 4850's are pretty cheap for the performance too.
***The fps estimates are based on my own observations of the chip while running 3dmark06 with an 8600GT 256mb, not crysis, and not with my 8800gt. I'll run a crysis demo with the 8800 as soon as it finished downloading.
EDIT:
Well, I keep crashing out of it, but I'm getting high 30's into low 40's for my average frames with the 8800gt. All settings on high, 1280x1024, no AA. About what I expected really, but I'd have to lower some settings and get above 45-50 minimum fps for it to match my requirements of playability. The game looks like it could be good, but I still wouldn't drop any coin on it personally.