the x850xt ati is kinda decent. it can hold CS source well but on Call of duty 4 you may need to super lower the res and graphics. My friend had one on his old comp and he was running a AMD 3500+ OCed to like i think 2.5ghz. but for a game like SC2 i doubt it. Try C&C3 T wars first and see how that goes. RTS games use hella alot of power.