<<If you own a D800 then I see no reason why you would want a D600.>>
Or in my case with my D700 why would I want one. Personally I feel that Nikon have gone down a silly route now. But, hey what do I know against Nikons very experienced sales research team! I have yet to see one single image that tells me that a D800 will give me any more than my D700. This IMHO this is a high pixel sell strategy trying to court the inexperienced or new amateur photographers.