I need advice on which telephoto lens to get

I have a canon 60D that I have owned for about a year now, so i'm a little new to this. I am mostly interested in photographing wildlife and my 28-135mm just does not cut it most of the time for getting good pictures of animals that are more than 5 feet away.

I am interested in getting a 400mm lens that has an image stabilizer and autofocus. f stop around 5.6. I cannot afford to get a lens that costs as much or more than my camera. My budget is around $500 and I don't mind getting a Quantaray, Tokina, or buying used.

Being a good macro lens is a plus too but not as important as picture quality. I want sharp photos.

Does anyone have any input for a lens that sounds like a good fit?

Thank you, Kelly