Yeah, kind of a step up difference between the D300/s and the D90.
One is a higher end soccer mom camera and the other is a good prosumer camera.
If price isn't an issue and you don't need the video feature go with the D300 and get some nice lenses.
And when I say soccer mom/prosumer I don't mean any are bad, shit, I've seen better pictures taken with D70's than with D3's...
I would suggest the D300 or D300s.