Hello In my country nVidia GPUs are known in my country more than ATI. I am working on game design and development especially FPS. I will choose from the 8800 series. But there are many types of this GPU: gt, gtx, gs, etc. Which one can i choose?? THe website of nVidia is full of broken links so i can't find any good info.

You can choose any card you want.

http://www.computing.net/answers/gaming/what-does-that-mean-gtgtxgtoxtx/7266.html

Comparison of NVIDIA Graphics Processing Units