I've been a photographer for a long, long time and my opinion is that a clean Canon EOS 5D Mk II would be the best for $500 or anywhere near it. Why? Because, of all those cameras you listed, the 5D Mk II, only this camera has served thousands and thousands of pro and amateur users with a very high level of dependability. I bought a mint 5D Mk II with the $300 Battery Grip for $500! It showed no signs of use, so I was very lucky. This particular DSLR holds the record for the most photo credits as published by ARIZONA HIGHWAYS magazine for perhaps the last ten years. When POPULAR PHOTOGRAPHY tested the replacement for the MkII, the new Mk III had slightly inferior scores for resolution and color accuracy. I don't plan on video use, which the Mk III does better, so I opted for the Mk II. Oh, also, my techs say that more than one Canon Mk II has gone to 2 million shutter actuations, which is very impressive. I have no friends at Canon, nor do I have any financial interest in a camera store. I've been retired for 20 years. As far as I know, there are no Chinese parts in this workhorse camera.