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@Remko - My lens line-up is currently DX oriented but I've been planning on making the switch at some point anyway, so I'm not really considering that as a part of my decision. My reason for the switch is mainly my desire to have a larger/brighter viewfinder and a desire on my part to move toward a more pro-oriented system - better build quality, etc. I have planned though, on keeping a DX body as a backup/teleconverter.
That does make sense. You will love the large and bright viewfinder from the D3 or D3x. Note that the viewfinder of the D700 covers only 95%, for me that was a showstopper, but your mileage my vary of course.
I went from a D2x to a D3 and was thrilled: more dynamic range, better at high ISO which for me as landscape shooter was a bonus: I could now shoot with a higher shutter speed and still at my chosen aperture when it was a bit windy. At base ISO the micro contrast of the D2x is a bit better though.
Think carefully whether you want a D3x. It is more diffraction limited and as the CoC is smaller, you have to either do focus stacking or use a tilt and shift lens for getting good enough DoF when doing landscapes. This is often overlooked.
Handholding a D3x is only possible with pretty high shutter speeds if you want a good image. If you do not want to use a tripod for portraiture, this might be something to consider.
And as already the D3/D700 are pretty demanding, the D3x needs top glass.
If you are not printing bigger than 17x24 inch, the D3 (and D700) will be excellent when using the proper technique (tripod, mirror up, cable release, good processing).
Good luck with making up your mind :-)
EDIT: as the pixel pitch of the D7000 is even smaller than that of a D3x, you might have experienced that a higher megapixel camera is more sensitive to handholding. And whether it is if any importance to you.