At this point seajewel I would just call it a day and sell the 600 on ebay. You should at least get $50-$70 for it. What did you pay for the 650? (Im guessing around $200, I just sold mine for about $205 a couple weeks ago) So you will be out about $130.
Good lesson learned.
I wouldnt let this cause you anymore heartache. It could have been worse and he could have sent you an empty box.
EDIT: Forget what I said I see you already sent it back. Let us know what happens.