I would be careful in buying a 20D. Until recently I had a 20D. Yes it is a fantastic camera, the image quality and available features are excellent.
However, mine had a problem with front focusing. Normally, this is not noticable. It became apprent to me when I purchased the Canon 100mm f2.8 macro.
I could focus the subject clearly, but the resulting image was always out of focus in the centre. I have read many reports about this problem.
I believe that this problem is more common than people think, but for a lot of people will never be noticed.