It's like walking into Best Buy and buying an Open Box item. They will tell you the same. You get the same warranty as brand new.
Haven't you ever bought an open box item at your local store and asked about the warranty?
That's what Denon told me. They also said, if your sales receipt has the word "Amazon" on there, you are good to go.
Who is going to mess with the biggest Super internet store in the world?
And which AVR company is bigger than Denon/Marantz?
I don't think Denon wants to risk their relationship with Amazon customer service over one AVR warranty.