For movies and Canon you need the 60D, the HD video on my 55od is very difficult to use meaningfully, because of the fixed screen. The 60D has the rotating screen which makes all aspects of photography much easier especially with live view.
As Dom says for motorsport you need at very least something like 70-200 and even that will be quite limiting, 100-300 or 100-400 gives you much better composition without cropping.
Grab QD's camera on the way to the ring and try and shoot a video, you will see what i mean about it being difficult.