Absolutely I would have a conversation with the dealer and the seller. Be extra nice but communicate that all you wanted were working speakers, as advertised by his employee. Communicate that you gave the seller the benefit of the doubt as well as a nauseatingly lengthy amount of time to remedy the problem. Explain that the seller represented his employment with the authorized dealer as evidence of his credibility. You extended the credibility because the dealer is a legitimate B&W dealer. If there is a representation problem, it actually exists between the seller and his employer as it wasn’t you who made the inference.
Now, explain that you are a man of principal and that you arent going anywhere. The last point is the one that usually results in a satisfactory resolution. Explain that you have no issue whatsoever with the idea of spending $100,000 in legal fees if they force you to chase this to ground. Its the principal of the matter.