Hi Beth, taking shots in a dimly lit auditorium is always hard! It might be worth trying to narrow down exactly whats causing the missed shots, by trying again or examining what happened in more detail. I think generally using a flash will introduce more delay. Focusing also introduces delays, especially in lower light.
What I'd recommend is a camera that can shoot good quality images at high ISO to avoid using the flash as much as possible. Also, I'd recommend buying faster lenses, f/2.8 or better if possible. If you're not too far away from the subject a 50mm f/1.8 or 85mm f/1.8 would be awesome.
So I'd say go for the 60D and some fast lenses. Or, consider going to a full-frame camera which will have better image quality at high ISO, you might be able to get a deal on the Canon 5D Mk II now that the Mk III is available.
