Yeah, I'd love a full frame too, but they are way out of my price range. If motorsports is all you shoot, then you might want to look in to a 7D, it's a crop sensor but great at shooting fast moving objects. I spent some four years on a 300D with kit lens and another three years on 400D with kit lens. I guess the kits have gotten a bit better now that they atleast have IS on them and slightly improved optics, but the difference to a kit lens when I got the 18-135mm STM for my 650D was... significant to say the least.
To avoid going completely offtopic, I'd advise the OP to stick with either a Canon or Nikon. They're easily the most popular ones out there, and that means cheaper used lenses so you can actually make the most use of the body.