Hello all.  I have an e520 with an existing 256Mb ATI Radeon X1300 Pro (No fan) PCIe x16 card, best I can tell.  I want to go to a 1Gb card.  Is a PCIe 2 card compatible with my mobo?  I don't want to over-buy if I am restricted by bus speed or Mb limitations.  Suggestions are needed ladies and gents.