I have the rebel xti and I'm in the market for a new lens. I'm looking for a lens that will go telephoto between 200-300MM. Looking to spend up to $700. I"m a pretty serious photographer with winning best in show, best in division, 1st and 2ed on every picture I entered in the fair this past summer (07) The lens that came with the camera just isn't working for those shots I need to get in-close anymore. Can someone else me out?