According to Denon, Denon Refurbished AVRs do not get full factory warranty; they only get 1 yr warranty. The new and open box 3312/ 3313 gets 3 yr warranty.
I couldn't care less about 4K, but I won't complain.
I had a refurbished Denon AVR that I had to send back to the NJ factory to repair under warranty. When I got it back from Denon, I plugged it in and turned it on. Few minutes later, there was smoke coming out of the AVR.
Yeah, I my experience, Denon OEM factory refurbished from NJ is NOT like new!