Kinda new to all this and there are SOO many lenses with different types of glass and all this.. Please help me out here.. I have a Nikon D80 with the kit 135mm lens. I'm looking for a few others.. I would like a macro lens, and a longer zoom lens. I'm thinking 70-300mm.. A very wide angle would be nice, but I think it can wait until last, unless I can afford it now.. I have a few questions before I buy.. 1. Sigma vs Nikkor.. which is best bang for the buck? I don't have a million dollars to be spending on lenses, but if there is a noticeable difference then I will wait and buy the more expensive one. 2. Used lenses.. Reccomended? They are cheaper, but is it worth it? 3. Refurbished lenses? Also cheaper, but worth it? 4. Any reccomendations? I want AutoFocus (I'm assuming on both? Right?), and Anti-Vibe on the 300mm. 5. Should I wait on the SuperWide angle? Which one should I look at? 10mm? 12mm? Sigma? Nikkor? What about the different types of glass? I even saw an ISO rating on a few lenses, does this mean they work with that ISO only? Even when the camera has selectable ISO's? So many questions, so many lenses.. Make sense of it please.. Thanks in advance!