I wonder how ebay would react if you file a dispute and give them a link to the other auction. I am sure ebay would be less than happy knowing the same item being sold on another site as well.
If I were in your shoes I would send the seller a message through ebay telling him you're not happy and why and also tell him if he does not handle the situation to your satisfaction you are going to file a complaint with ebay and paypal and let them know why you are not happy with the item and will also tell ebay and paypal about the fact he tries to sell one item twice. And tell him you will send the other auction house a mail similar to the one ebay will receive.

Good luck and keep us posted.