I think I'm finally purchasing a Nikon D80 this weekend. Which would you prefer in terms of lens combinations? Here are a few that I am looking at: Nikon 18-55mm Nikkor 80-400mm Nikon 18-55mm Nikon 70-300mm Nikkor 18-200mm Sigma 170-500mm Nikkor 18-200mm Sigma 50-500mm I've read lots of good things about the Nikkor 18-200mm lens, so I'd like to go with one of those combinations. Does anyone prefer either the Sigma 170-500mm or 50-500mm? I'll be doing mostly wildlife/bird photography, so I want something with good range. Is the picture quality with the 170-500mm better at all than that of the 50-500mm? Thanks so much!