For example, many of the big retailers say that their Nvidia GT 640 cards are pci express 3.0 interface cards, but since I've read that even higher end cards can't entirely use the pci-express 2.0 interface, what is the benefit of having a lower end pci express 3.0 interface graphics card? - Do they have something that makes them use the pci express 3.0 interface more economically, better, etc... I know that the gt 640 has a Bus Type for PCI-E 3.0 (all except the 192 bit) what does that mean for performance?