If you have full frame lenses, then the D700 would be the way I would go, otherwise if you don't, and if selling those DX lenses will hurt your pocket (a DX lens on a 12MP D700 is silly), the D7000 is a great camera, a step down from the D300 in some ways, step up in many ways, but you know that.
Photokina is happening in a month, fairly strong rumours about of a D300s replacement are were flying around a few months back, may be ideal for you - high end DX body. If you can wait to chance it, it might be something that would interest you, though as always it might take a while to hit the shelves if it is actually released. Prob cost near enough what a D700 is getting.
