Good point about the D300.
On one hand there's no reason to sell the D2X - it still is as good a camera as it was, but on the other hand, there is a compelling reason to replace it with a D300 as a 'backup' to your D3 (or as a DX frame hi-pixel density body when you need it) in that you can exchange the picture control settings between bodies, plus the D300 is better at hi ISO. I initially was lukewarm about my D300 (being a D2X owner), but as of late, I think I've finally tuned the camera in to where I like it, and couldn't be happier with it - it's an amazing, and overly flexible, machine. It can easily be set to produce garbage images just as it can be set to produce amazing ones (technically).
As for the 14-24 - to be frank, it's going to be an agonizing tradeoff decision for many folks - from a purely image quality perspecitve, it is most definitely better than even the 17-35 I've raved about for years - except at 24mm, where the older lens has an edge in the corners and thus it's a "wash". I own both, and have tested the new lens quite a bit (3 test scenarios on three seperate days plus a "real" photo shoot - that's a lot more than some guy trying it out in a store or making a brief snap judgement about it) against the 17-35 and I am extremely confident in my opinion that it is to wide angle lenses what the exotic telephotos are to the rest of the range - it's seperately and distinctly just a markedly better lens, period. But the trade off is that no-filter thing and it's propensity to flare in some point source light conditions - so for some folks, that right there means it's a no-go. I'm more a studio shooter who likes wides on a DX frame for distorted art/fashion that is my particular style, plus the occasional landscape where the sun isn't pointing into it, so the 14-24 is absolutely my kind of lens. But I keep the 17-35 around too for times when it's the better fit.
-m
(lots of beer for instance).