70-200mm f/2.8L (non-IS)
This would be one of the best lenses for your use. It doesn't have IS assistance and it is a bit on the heavy side but, for focal length and aperture it would probably be the best lens out there. This lens would be a great combination on your 40D, especially if you opt to use a monopod.
Not knowing the light level in the venue at which you are shooting, it is pretty difficult to make a calculated guess as to what your exposure might be. However, there is no zoom lens with a faster aperture or any zoom lens which has faster auto-focus (not the same thing) than the 70-200mm f/2.8L.
The 70-200mm f/2.8L lens should be within your budget or just above that budget price. Purchasing used, should bring that price down several hundred dollars.
On the other hand, I use my 70-200mm f/4L IS lens for just about any type of shooting. It is a stop slower than the f/2.8L but it is lighter in weight and IMO more versatile, in that I can hold this lens at slower shutter speeds than I can hold a non-IS f/2.8L. If I were faced with shooting this type of activity; I suspect that I could get along just fine using my 70-200mm f/4L IS lens at ISO 1600 or so.
I think that you will find that the 70-300mm f/4-5.6 IS lens doesn't focus as fast as you might wish in lower light levels. Additionally, the lens closes down to f/5.6 pretty quickly as you zoom. IMO, f/5.6 would be jut too slow for your purposes.