I googled the venue--looks like you could get stuck with seats further from the stage than you might like. You'll probably want a lens with a good reach then, with a relatively large aperture if you must handhold.
Assuming you can get these before April, a few good prime (not zoom) lenses might be the DA70 f/2.4, FA77 f/1.8, FA100 f/2.8 macro. These aren't cheap ($450 and up), but are good. There are also third party options in these focal lengths to be found at B&H, Adorama, etc. You could find older (especially manual), and third party options as well on eekbay, or KEH (.com, I think).
As far as zooms, there is a Sigma 70-200mm f/2.8 if you want to go that route. There are also zooms (if you can find them) that cover a walk-around range of about 28mm to low 100's+, but image quality tends to suffer with super-zooms. There aren't that many f/2.8, but you could find some f/2.8-4s/3.2-4's. If you can take a smallish tripod into the venue to set up at your seat (it could be pretty inexpensive if you aren't going to hang a monster lens off the camera, and are prepared to get a cable or wireless shutter release as well) you might be able to stretch these "slower" lenses. A DA55-200 f/4.5-4.6 is a good all-around option (great for shooting outdoors), but you might struggle in a low light venue without some sort of camera support (+external release to eliminate camera shake).
I'd expect you'd find some motion blur in your subject though. Motion blur can be creative, and cool sometimes, but that may not be what you want. Then again, the stage light could be really friendly --but you'll still probably want the reach.
Last edited by bdavis; 03-18-2007 at 11:23 AM.