I was able to run Crysis 2 with highest performance settings (Extreme) in Singleplayer mode without a single lag and smooth gameplay.
In multiplayer I play with "Gamer" settings, because mp seems to need more performance.
My Hardware specs:Core 2 Duo 6420 4 MB Cache
3,2 Gig DDR2 Ram (damn you mobo)
Nvidia Gefoce GTX 260 - 796 MB
WD VelociRaptor 10.000 rpm
Win7 x64
Power supply: 550W with manual PFC
FullHD Led-TFT (1920 x 1080)
Some parts of my hardware are already a few years old, but still runs Crysis2 smoothly

What power supply are you getting? I was on my Highlander PWR but I after getting my new gtx I had to change it and I wonder what to get now, I know that my highlander won't last long anymore, it's only 750W. I need a 1000W supply, but no one is yet to give me a tip what to get.
Also don't listen to the haters, they just envy 
Good choice with getting SSD for system drive, bad idea taking an radeon, I am more of a Nvidia fanboy
, haven't had a radeon since the old 9500 series 
I recommend power supplies supporting "PFC" (Power Factor Correction) and overvoltage protection.
Those are a little bit more expensive, but your hardware will thank you (much longer life and thunders can't just break your PC).
Hardware like Ram and GFX-cards are really sensitive against power fluctuations.