Upgrade for CS:GO?

Hi,

I have a 120hz monitor, but it's kinda useless since I only get 50-80 fps in CS:GO, L4D2, and TF2 !!!

What the heck do I have to do to get 120+ fps in multiplayer?

My current specs:

AMD Athlon X3 455 (3.3 ghz)
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Asus Radeon 6850
8 gb ram
550 OCZ Fatal1ty PSU

Upgrade to Phenom X4 965?
Upgrade video card?
Add a 2nd 6850, get a beefier PSU?
Upgrade cpu and mobo to i3/i5?

Any help is appreciated, thanks !

Also, I play on 1024x768