Which graphics card set up is better, 3x Gigabyte HD6850's Overclocked vs a Gigabyte GTX580 super overclocked?

Of course the 3 HD6850's will be in crossfire and the GTX580 will be running by itself, both setups are around the same price|||3 6850's will beat the 1.5GB version of the GTX 580. But a gtx 580 3GB will beat all of them down.|||:O YOU FOUND A MB WITH 3 PCI-e SLOTS??? Damn, don't waste it, use the triple-set.