First off, I think you need to be willing to expand your budget to a minimum of $500. For shooting low light subjects (i.e. anything in a theatre) you are going to really hate life if you have a point-and-shoot camera. I would start looking at DSLR cameras like the
Nikon D40 or whatever the equivalent Canon is (as a Nikon person, I don't really know the Canon line). You can pick up a
D40 kit with a decent lens for about $410. That kit will get you pretty far, but eventually you will find that you will want a different lens.
The real key to shooting in low light and theatre, as has been mention, is a good tripod and fast glass. You need to let as much light get to the sensor as you can. What you are looking for is lenses with a low number f-stop rating. The lower the number, the "faster" the lens, and the more expensive it will be. Next time you have money I would look into a lens like
this. The best thing about getting into the DSLR world is that you can upgrade lenses as you need them.
Other advantages to DSLR cameras are larger sensor size (thus better light sensitivity), faster power up, interchangeable lenses, faster shooting speed (no lag between when you press the button and when the photo is taken). If you are serious about getting into photographing your work, the DSLR will be your friend. Plus, you will love to have it for every day use!
EDIT:
It just occurred to me that if you want to go P&S you should look at the
Canon G10. This is a very full featured camera yet it is compact and easy to use. It functions almost like a DSLR.