Ok so I am planning on getting a lens for action shots, mostly cars and motorcycles on the track. Generally it will be sunny, but as weather goes its not always sunny. I have been looking at the 70-300 f/4-5.6 IS and the 70-200 f/4L. I talked to my local photo shop and they suggested the 70-200. I know there are some 3rd party lenses but I don't know anything about them, so if you have any alternatives, please say so. As far as price goes, I would like to stay within $100-$200 of the Canons. Preferably the lesser end. I am on a budget.