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I have a Canon T1i, but now they are up to the T3i. Those are the top "amateur" cameras I found. To really capture the stop action, you need a good lens. I have fixed 85mm f1.8 that I use and it works awesome. Especially in poorly lit high school gyms. I know lots of guys that have the f2.8 lens and those are great if the lighting is semi-decent. anything less than a 2.8 and it'll be "iffy" at best.
The 85mm is a great lens!! I sometimes will rent the 2.8 70-300 for competitions. Great for getting close to the action. I would definitely advise spending more on the glass if you have to prioritize. I definitely love the challenge of photographing cheer!