hamjam When you get to the camera store, spend lots of time with each camera. Hands On is extremely important and the main reason I prefer the D800. If you do not shoot for long periods of time it will mean less to you.
When I first got my D600, I thought being smaller and lighter would be great. But the D800 is not that much heavier and after even 6 hours of shooting I am less fatigued because the camera and controls fit my hand much better.