I noticed that whenever I see nvidia graphics cards on sale, they are made by a 3rd party manufacturer. For instance, the new 7800 GT that is a $400 upgrade option in the new powermacs I saw at fry's for $350 this week (Nvidia geforce 7800 GT 256MV GDDR3 PCI-EXPRESS video card by BFG). Are the cards that come in BTO powermacs from apple pretty much the same as these 3rd party cards? Are all nvidia cards branded by a 3rd party manufacturer? The most important question would be - if I decided to upgrade a card in one of these new powermacs, how could I tell which cards would work (ie, do all of the pci-express cards work, or would I need to flash the card or buy a mac edition of one).