If this question seems ridiculous ease forgive me, but I was wondering what the real world difference between the ATI radeon 5770 & 5870 cards is? I have a Mac pro 1,1 and it currently has dual GeForce 7300s in it. I'm looking to upgraded the main gnu to something better and these cards seem the best right now (if they work in the 1,1) Does the 5770 card work in the 1,1 model? A comment on the Apple product page says it does since ATI bundles support for both EFI32 & EFI64 in their cards, but I'm still a little wary. Lastly, if the Hd 5xxx cards won't work in the 1,1 model, what would be the best upgrade option for me?