Use the supreme commander core maximizer, also keep playing till the late game, the game will consume much more cpu power later on and really benefits from a quad core.
Crysis and UT3 don't really need that much cpu power, even 2 cores is more than enough for them.

) I recall in the normall supcom in skirmish I had some lag in the late game with 6 players with each having about 800 units.