I bought the S630 because it’s the newest version pretty much. It can play all CDR's which is good because I use a lot of burned CD's. I think there are other differences, but it being a brand new and current model made me want to get it. The problem I believe is that the unit was DOA as SCLJA said. I tried to bench test it and it didn’t work. That may or may not mean anything because its possible I was doing it wrong, but the bottom line is I couldn’t start it up on the bench. The place I bought it from said I could return it which I am going to do. SCLJA said that the S630 works in these cars and I trust him. The S620s are tempting because they are cheaper. And more than likely they will work just fine. But I’m picky so I had to have the newest version. The fact that it was brand new factory sealed was what really turned me on.