It seems CoD doesnt make good use of >2 cores, so believe it or not, your CPU might be acceptable for CoD (especially if you tried overclocking it). From
my testing, it seems the amount of videocard memory ought to be your primary (secondary and possibly tertiary) concern. If I where you, Id buy one of those oddball 3GB nvidia cards and keep the rest for now. It might actually run the game fine. If not, you can always spend the money later.