Hi fellow CSers, I just got my 50D along with a 50mm f/1.8 and a 70-200 f/4L (non IS ) Anyway, what do you guys think of this combo? Can you guys recommend me a lens within $300-$500 that can take wide angle shots? And hopefully (not a must) cover the gap from ?-70. Was looking at the Sigma 17-70 although it overshoots my budget a little. What do you guys think of that lens as well?