The Mythic and Legendary map packs for Halo 3 both cost 800 each. The Cold storage map and the Heroic map pack are both free. And the the Map Pack and mode pack (contains that reinforcement mode, another mode like capture the flag, and another where you win for having and keeping the largest army) for Halo Wars also both cost 800 each. So all together, you're looking at about 3200 Microsoft points. I recommend buying the 4000 point card, and you will still have another 800 left to buy something else.