I have a Via SG3 Unichrome IGP, built in a KM400.
I have the black terrain and leaderfaces problem. I dont own a copy of civ4, but made tests with someone copy in my computer. So I'm not worrying about lost money.
After all, Age of Empires III runs fine here, except in naval battles, where the water splashes slows the game so much that is impossible to play. No black terrain, but the game will get boring when the campaigns ends.
Nvidia and ATI are monopolies. It's like Intel vs AMD.