Salute
Best card for the money is the ATI 6950, it has 2 gig's of VRAAM, something which CoD really benefits from, it can be overclocked to 6970 performance quite easily and is not an expensive investment at $239.00.
http://www.techpowerup.com/articles/...ng/vidcard/159
http://www.newegg.com/Product/Produc...i+6950&x=0&y=0