There is a $300 rebate on a D300 and 18-200VR combo right now. You can get the kit for $2,150 (
Adorama price). The lens is not the fastest, but because of the VR you can use lower shutter speeds and its just like using faster glass. And its not like its a slouch of a lens in the first place. I say stick with the D300 and the 18-200. The d300 has several advantages over the d90 and d200 for future use. I just ordered a d300 body for myself. Was torn between it and the d90 and once I compared the features the extra $500 was worth it in my opinion.
If you think about it. An 18-200 zoomed out and at 5.6 according to Nikon you have a 4 stop equavilant advantage with the VR on. That means you could actually shoot at 300mm equavilant (crop factor) at F8 and still use the same shutter speed of a 300 2.8 lens wide open (since they say 4 I am betting 3 stops is probably more practical). Not shooting at wide open on the 18-200 will give you slightly better pictures (closer to lens sweet spot).