Low cost one :
-E8400 (very O/C-able)
-9600GT (1GB version is not a luxuary, depends on your monitor and if you want keep the configuration for a long time)
-2GB ram (3GB is more confortable if on Vista)
Bit more expensive and powerful :
-QX9450 (very O/C-able)
-8800GTS O/C or 9800GTX (basically the same). GX2 is not worth unless you run your game in low resolution (lack of ram for SLi framebuffer in AFR, and so for AA+filtering)
-4GB ram







