Welcome to Nikonians! The choices are many. The D7000, like your D50 is fully compatible with All AF Nikon F mount lenses with the exception of the 80mm f/2.8 and the 200mm f/3.5 made for the F3AF back in 1983. What is your budget? Do you want to replace your Quanteray 18-200mm? Good Luck and Enjoy your Nikons!