<<I suppose if I were to sell my D700, I could also argue that for less money than it would take to buy a D7000>>
That certainly doesn't apply in the UK. Here, a new D7000 can be bought for £700 (approx $1050), which I think must be a record devaluation of a Nikon camera from new, about 37%! However, Nikon D700's are still being sold in high numbers on e-bay and they are averaging about £1000 (approx. $1500) which shows how highly thought of the camera is.
I am interested however, apart from the slower fps issue, why you don't seem to see the DX mode on the D800 as your DX camera. I ask this as I am looking to be convinced that the D800 in DX mode will, apart from the faster fps issue, do the job of an APS-C camera.
I would be interested in your experiences of the D800 in DX please?