I have a budget enough to buy either a D700 body or a D300 body and a 70-200mm f/2.8 VR, and I need help deciding which one to go with. I currently have a D40 with the kit lens and the 55-200mm f/4--5.6 lens. My primary reason for upgrading is to be better able to photograph dance performances, i.e. fast action in low-light. Based on what I've read, it seems like the ISO upgrade from the D700 is enough to warrant spending the extra money, but I don't have the money to get both the pro body AND the pro lens (yet). Will using a consumer level lens hamper the pro body so much that I shouldn't bother?