The Warranty is good as long as you are the 1st owner (original buyer) of the unit. The dealer with the display model is correct, as long as it was not a return from another customer.
If the C50 was "recently" discontinued, McIntosh will honor the warranty. However, Mcintosh will be quick to inform you that they will NOT honor the warranty if the demo model was discontinued beyond a specific period of time. Don't believe the dealer, call McIntosh before you buy it. Otherwise, your warranty will be from the dealer only. Believe me, I learned the hard way.