Vid Card question

I am considering building or buying an I7 computer that I 5box on. Anything is going to be better than the AMD64 3200+ that im on now. But I am unsure on which vid card would be a good bang for my buck. I currently 5box now and want to get a system that can easliy 5 box in Dal and give me the option to add more characters to my team if I ever want to move up from 5.

With an i7 and good RAM+SSD, anything over an NVidia 260/AMD 4870/NVidia 9800GT will be overkill.

When considering DDR3....1333, 1600, or 1800? I will not be overclocking this system.

I went with 12gb of 1600, it was a tiny bit more then 1333.