You can't say ATi or nvidia is better (No such thing as geforce, it's nvidia) and $100 won't get you a decent card for gaming, espcially with those up coming DX10 games. If you really have to use only $100, go for a ATI Radeon X1300 Pro. But, if you want to play latest games at high settings, you need a budget of around .. $400 atleast. The ATI Radeon X1300 Pro will be a slug for games nowadays.