Gaming Pc - Modification

Hello,
Now i have a:

CPU: Intel Q6600
GPU: Nvidia 8800 GTS
PS: Thermaltake 850W
Motherboard: Asus P5K-E
Case: xClio A380 Black
Monitor: 22'' WS "SAMSUNG 2253Lw"
Ram: 4GB
Cpu Cooling: Thermalright Ultra-120 eXtreme /w 2x 3000RPM scythe fans
HDD: 1x 1TB WD, 1x 500GB WD

And i want to upgrade a graphic card to a 660Ti or something else with similar price. I only want nvidia. Also i want to buy an ssd drive. Games that i wanna play are Bf3, Mw3, Gta4 and 5, Black Ops 2, and other. If you have any other suggestions let me know. I am from Poland if that matters. You can use newegg for links.

Thanks in advice,
Lukasz