what would you do?

Checks should have been done as soon as the amp was received. I don't think your friend has a leg to stand on since it has been over 1 year. Some high volume dealers may mix stuff up but most of the time if they deal in high volume they have good inventory control.

Also as long as they got a Cary v12i amp and not a totally different amp then what is wrong if the serial numbers are different? Is each Cary amp customized or is this amp a collectors item where having a lower number from the run matters? I'm just confused as to how the serial numbers would really matter in this situation.

Your friend could try to talk to Upscale Audio but even then what can they do? The other Cary v12i with the serial # might have been sold already. It has also been over a year.

I think your friend may just have to enjoy the amp he has.

Why did it take you a year and a half to figure out the purchase was wrong, and why come on pinging a dealer without asking him first?

Sorry but just a little confused. Who buys amps based on a serial number? Every piece of equipment that I have bought new was by a model number; not serial number. If the carton was sealed, good enough for me. The only time I could see this being important is if you were buying a used amp and there were two identical ones out of their boxes that you auditioned. You liked one better than the other, picked it, and the serial number was the only way to differentiate between the two. Was this the case? Was it a used purchase? I cannot imagine in a new purchase a serial number would matter as long as you got the right model you were purchasing. Am I wrong? If so, can someone tell me why?

You are going to need a lot more proof to paint Upscale audio as anything but a A+ dealer. What did Kevin say when you called him, that's all that matters.

Several years ago I bought a blemished (B stock) record cleaner from him at a discount. When i drove out to his shop to pick it up, his staff couldnt find the B stock item so they sold me an A stock at the same price.

Phenomenal customer service.

Not dealer's problem - yours. You should have verified when you received the amp and discussed with the dealer then. Not now. Sorry, way too late. Dealers are people too. People make mistakes. Bring it to their attention within a reasonable time frame (1.5 years is not reasonable; more like within a few days of receiving the piece) and give them a chance to resolve.

Had you done this 1.5 years ago and the dealer not resolve, only then would I consider the dealer a dirty player.