Since I'm buying a new lens that cost more than my camera body did it brings up a question I've had for awhile that I'm hoping some of you can clear up for me. I have a Nikon D40. I know some lenses don't auto focus on it (hence why I'm spending so much on one that does), is this a smart move?? Is there any reason other that more fancy options that I should upgrade my camera body?? I'm VERY happy with my D40 and figure I'd spend the money on glass, lighting, props, etc.. instead.