Hello Jason, and welcome to the friendly Camera Labs forum!
To enjoy your stay here please have a look at the house-rules
As to your question: I'd focus on lenses: Is your collection of lenses FX-ready? If so you have two options imho: save up for the D700 or wait for its successor (which will certainly be even more expensive). The D300(s) is almost outdated as the D7000 clearly shows what the latest sensor and processing technology from Nikon can do. That would also be my recommended alternative: The D7000.
But really: You have to decide at one point whether you're aiming at FX or are content with DX.
Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews
, My Pictures
, My Photography Blog