when You buy a card for a mac does it have to specify that it is for mac ? or I can just get any brand that is a gt 640.. I dont really understand how the whole gpu thing works. I own a mac pro 3,1 2008 2.8- 8core I want a graphics card that would enhance my adobe premiere pro editing. any help would be greatly appreciated. thanks. i'm on a budget so please dont suggest any 300 dollar video card. thanks !!!!