I'd check out the AGP 4x compatability of the 6800 cards before buying...and whether that impacts on the performance. It's a bit wasteful buying a ferrari if you can only use the first 3 gears... imho
I'm tempted to suggest that you stick with it for the moment until AM2 is realeased (might have more graphics card updates soon too?
) and then re-spec a new system out?