Budget is going to be key and working out how much value a certain camera will add to your business.
Jim is right about the D3 it is a lovely piece of kit but you are going to lose 1.6x field of view from using your 10D so to get the same view as the 200mm lens on the 10D you would need 320mm on the D3. The D3x has a cropping when shooting at high speed but just look at the cost.
If you are going Canon then the sports option is the 1D mkIII, this is my sports shooting camera, I also shoot with a 5D for wedding/studio work. The 1D mkIII has a 1.3x crop so it is somewhere between the full frame of the D3 (and 5D) and the 10D. The AFsystem on the 1D mkIII are a lot different to to that of the 5D mkII making focus quicker and better for tracking moving subjects which is going to help you get more saleable shots.
Going back to the question of budget and how best to spend it make sure you are looking at the total package that you can end up with. To get better lenses and still good performing body you might want to look at the Canon 50D or Nikon D300 which should leave quite a lot of extra cash. Obviously if the budget is there then you can discount these options.