One question, as I've never upgraded a card before, I've always just upgraded my entire rig at once, will I need to uninstall my old drivers before installing the 6890? I just recently d/led the newest drivers for my card, but I'm sure they aren't the same. Or can I just unplug this card, pop in the new one, and will it automatically delete the old drivers and install the newest ones/drivers provided on cd?
Download the latest drivers from AMD. Uninstall your old drivers. Reboot. Install the new drivers.
Were you able to successfully unlock the fourth core on that X3?