Hello manus, and welcome to the friendly Camera Labs forum!
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I've deleted your double post from the 70-200 review-thread, as double-posting is a no-no on this forum.
Regarding your thoughts about getting to 400mm I have the following advice:
- the new Nikon 80-400/4.5-5.6 is certainly the option that produces the highest image quality of all lenses that you consider.
- the Sigma 120-400mm was not bad, but I didn't test it on a D800.
- The Nikon 70-200/2.8G VR II also shows some limits with the 1.7x converter, but actually is not too bad on a D800. Using this combo on a D600 might deliver some satisfying results.
So it is as it is most of the time: investing more gives you better image quality.
Sorry to have no "definitive" advice for you.
Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews
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