My sister has a choir concert coming up next month. It's going to be in an auditorium that's pretty dark but the stage is well lit. From experience, on stage the lights are almost too blinding, but that could be the fact that I had a trombone bell on the left side of my face 4 years in a row. The venue doesn't allow the use flash, but they do allow monopods, as longs as it's unobtrusive. I plan to purchase a telephoto lens that's around the focal range of 70mm - 300mm. Preferably, a fixed focal length but that clashes with the my target price. Which is $150-$200. Anyone have any good recommendations for a lens? I don't mind pushing my ISO up to 3200, or 6400 if needs be.