I think you should seriously look at the 1Ds MKII (not to be confused with the 1dMK2). For lens, I would recommend to go with the 300 f2.8 IS instead of 70-200 f2.8 IS.
Obviously, and you MUST buy a Nikon D200 with a 300mm f2.8 VR lens for sports. When your done with that, come on back and we'll help you spend the next
ten thousand dollars.
Seriously, in what way is the 300D and your current lens collection limiting you? In what conditions are you currently hitting the limits of your hardware? Are you sure its not technique? At one time, a slr camera was an slr camera, your lenses and skill were the biggest contributor to your results. Now that the "film" is a permanent part of the camera body people are going beyond nuts nitpicking the technical merits of each camera model.