As one who worked for the USPS for nearly forty years,and yes I still have some brains left, the buyers story seems dubious to say the least. My first question to you would be were the speakers insured by FedEX for their full value. If they were and the buyer is claiming that they were damaged, it is FedEx's responsibility to pay the buyer. Therefore the buyer would be required to submit a claim with photos of the speakers and all the boxes. If the outer boxes were not damaged, the buyers story of damage by "speakers bumping against each other" or any other "damage in shipping" story holds no credibility, and FedEx would tell the buyer to take a hike. If you want to be a nice guy, which it sounds to me that you are, and if the price of the grills are reasonable, you may want to refund the buyer the difference and call it a day. However, grills are expensive, I would tell the buyer to deal with FedEx.