I currently have a Cannon Rebel XTI and take pictures of sporting events - Football, Wrestling and Baseball. The camera works great for everyday type of use, excellent for day games but sucks when the lighting isn't perfect.

I have been looking at the 20D - finally affordable, but what can I do to take better pictures when the lighting is not perfect? Is it a lense thing or is a shutter speed thing?

I am tied to the Cannon series because of the heavy investment into lenses.