Just for clarity, in the discussion Steve referred to I was discussing 24mpx DX. The D800 is 15mpx DX. Big diff. It's only 10% more pixels in linear dimensions than a D300/D2X, and less than a D7000.
And I was discussing that mainly in the context of those that think pixel density is fully equivalent to focal length increases. That is far different than "good enough" for any particular expectation or purpose.
I have yet to be wowed by high quality D3200 images showing that this can be done. But I haven't searched hard for that. Love to see the links, especially comparing something like D300 at 300mm verses D3200 at 400mm, original pixels, showing identical image quality in real world wildlife dynamic images.