Well considering the jump from the 460 to the 570 on Cataclysm is 20 frames per second, with the 460 being 60 frames per second higher than the human eye can actually see....I think that it's kinda a bit overkill personally.
I can run WoW on medium settings on my netbook, to give you an idea. (1.6ghz atom processor, 1gb DDR3, integrated graphics)