What is the fastest video card upgrade for a mac pro?

i want an extremely fast video card that would max graphics on all games on my mac pro - newest version|||You can get Radeon 6970s working but you have to flash them and there are issues. The new Mac Pros, which are expected to be announced this week now, will probably use them and thus there will be an official version in a few months for Lion.|||Upgrade the video on a mac pro?? Dream on buddy