what would you do?

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.

The old bait and switch or maybe the shipping department made the error of sending you the wrong amp. I would expect better from a dealer and its too bad it took over a year to discover.

A few years back and reluctantly I purchased an Aragon 4004 MKII off EBAY. After receiving the amp I noticed the MKII sticker was not on the back of the amp. Contacted the seller and he said the sticker had fallen off a while back. I determined later it was not the MKII but I was charged the higher price for the this version. I have not made any more purchases on EBAY. "The EBAY gang rides again!"

"The old bait & switch" Upscale Audio is not ebay pot luck.

And, as others have said how could the poster not realize for a year and a half that he received the "wrong amp"?