Have an HP m8100n with one available PCI-e x1 and one available PCI-e x16 slots. Wanting to upgrade to GeForce 8800GT but all the video cards I find at Newegg, for example, show that they are PCI-e 2.0 x16 cards. Do they still make just PCI-e x16 cards? Will the 2.0 cards work in my computer? Also, need to upgrade my PSU. Will one with 550 watts be sufficient? Thanks for the help.