Canon 450D is your other option within your budget.
The thing is though:
You like Cameras
You take a good few pictures
it seems to me you live in area that you can take some cracking pictures .
You say it's your last big camera purchase.
Well make it a good purchase spend a bit more and get yourself the D300 and a decent Tripod.
You can build up on the lenses.
Sigma are often better than Nikon now for their lenses.
Weight of the D300 is not that bad I use ours
and it has the battery pack on and when the big telephoto lens is on it can be heavy but still usable.