Ready to upgrade D70 and/or glass
I went from a D70 to the D90. It was a good upgrade in terms of resolution and better ISO performance. The D7000 is even better in both those areas.
I suspect the reason you are cropping a lot is because of the limitations of the 18-70. Yes the 2.8 zooms are great, but there are lots of great lenses. Take a look at the Nikon 70-300VR - it 's a great lens and super for the price. AF-S so it will focus pretty well.
You might want to look around at the used market as a lot of folks are trading up to the latest and greatest, but the old lenses still perform just fine. 180 2.8 is just a staggering good lens, though a bit slow in focusing by modern standards - though I shot college sports and we didn't even have autofocus . . . I also know people who do HS basketball with an 85 1.8 and get great shots.