I understand x RELIC x your position but I have transacted on eBay many times and sure enough, I agree with you about using authorized dealers however if he chooses to pick the SquareTrade 3-year warranty, then it is SquareTrade's job to chase the vendor and SquareTrade will associate themselves with good vendors, they also guarantee a 5 day resolution. I have used SquareTrade for years for my Apple and eBay stuff and when my phone broke, I got a replacement within 5 days, that is their guarantee.
The vendor provides 14 days return policy and eBay protects the buyer within the return period, you can raise a dispute with eBay, they'll side on the buyers. So don't feel that you do not have protection because you do and you can get a case opened with eBay if the vendor does not deliver, they hold the money with PayPal until the goods is delivered and the goods has not been marked delivered so as a buyer you have the last say as to when you got the X5 shipped.
My suggestion, contact the vendor and require that he gives you a delivery confirmation, look at the vendor reputation and reviews, then pay using PayPal (that is very important for your protection) and buy the 3-year warranty from SquareTrade, you'll beneficiate from anything happening to the DX50 (failures that is) for a 3-year period. By the way the warrantee is cancellable with the portion unused being reimbursed, a perk.
Good luck but don't be phased but that.