Technically, ATI cards will be able to play "The Lost Coast", but not with the pretty HDR effects enabled. ATI users will see the same graphics that are seen in the original HL2, which are not shabby at all. I think the new HDR effects combined with the higher resolution textures of "The Lost Coast" gives it an Unreal 3-esque look. It will definately be the finest graphics seen in a game to date when it comes out.