What is it you will be looking for in your next camera? Will it be a replacement for either of your current cameras, or an addition? How often do you need/want to shoot at more than 6fps?

I wouldn't worry about noise levels from either D600 or D800 - if you're happy with the D7000 and D700, you should be happy with either of them on that front. And personally, I wouldn't let the hysteria about AF or dust problems affect my decision.

But from the information you have given us, I would suggest that a used D3s might be a better fit than either D600 or D800. You'd get the higher frame rate and even better noise performance than your D700, without the apparent penalty of larger file sizes.

Brian
Welsh Nikonian
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