The 5D3 is a great camera, I love everything about it but need more speed. Shooting Motocross and Downhill these guys are really really fast, and if something happens I want to make sure to get it. Im just wondering how is the 1D Mark IV AF against the 5D3 in sports. I tested the 7D the other day at the local shop and its AF was super fast and the 10fps was great, but I know its a hit in image quality and lowlight shooting. I can afford a small hit but I still need sharp images that are good to print if they need to be. I plan on more MMA shooting this year as well so It does need to do High ISO at around 8000 and be usable.