nVidia GeForce FX5600 8X 256MB - Pro View
ATI X800 Pro 256Mb - Sapphire
Now my first conclusion is to go with the ATI as its a pro card.
But I know very little about the other card.
And I have a Fatality FS-V7 kit given to me the other day, not usable with the FX5600. Its whether to use it on the ati and overclock or leave it be and sell the kit.