How long have you had it? Most warranties even 2+ year ones usually have some clause of 30 to 90 days for full refunds. If you have used it over a year, then a new B stock will be a replacement in better condition than the one you lost, so you would have a hard time claiming they are ripping you off. Read your warranty. What does it say? You can probably find it on the Harmon website if you lost it. You also have to wait and see what Harmon does.
Giving a new B stock replacement is a common industry practice. They have made you whole, when all they are required to do is fix the old one.