PCI-E 2.0 is a new version of PCI-E X16. You do not need a mobo with PCI-E 2.0 right now; most manufacturers just started making them. The ATI Radeon 38xx series is PCI-E 2.0 based
PCI-E 2.0 cards are backward compatible. 2.0 is just double the bandwidth, which....if I'm not mistaken.....can't even be utilized fully by current hardware.