There is a store in my country which gives various rebates when a graphic and is bought along with a GPU.The two cards I am interested are the XFX 6790 and XFX 6850 Black Edition while I am going to buy a 600w Cooler Master psu .Here is a break down of the costs
6850 Black Edition:
Card Price: 18000
PSU Price: 5100
Final Cost 22300
I would recommend you get a cheaper card like the 5770 if it is available and spend the extra money on more system memory. It is important to have a balanced system for smooth gaming and you are a little lacking in that area. While you are thinking about your video card purchase see if you can budget in a memory upgrade as well or your frame rate may still be low or very sporadic. I noticed a big difference going from 2 to 4 and a minor difference going from 4 to 8. I still however recommend getting the highest density you are able to afford because there is really no such thing as too much ram.