If you have AFS lenses (with the focusing motor built-in the lens), I'd go with the D40 or D40x. Don't be fooled into thinking 10mp is a big advantage over 6mp on the D40.
http://www.kenrockwell.com/nikon/d40.htm
http://www.bythom.com/d40review.htm
Between a D80 and a D200, it sounds like you'd be better off with the D80. It's smaller and lighter, and has the program modes. The D200 has a metal frame vs plastic, weather-sealing, can meter more lenses, and shoot 5 fps vs 3 fps. It is a lot more camera. Those links above for Ken Rockwell and Thom Hogan have plenty of information on the D80/200 as well as dpreview.com.