The refurbs at A4L come from a factory designated facility that does repack them in new boxes and makes sure basic accessories are still with it (sending it back overseas to the actual factory of course wouldn't be feasible
). It isn't the same box as a new unit, tho. Sometimes a refurb has limited warranty, sometimes it has a full warranty (3 years is all the better Denons would come with new unless that's changed recently).
That said, I did have two bad Denon refurbs from A4L (on a 4520) but they took care of me and I ended up buying a new closeout instead for $100 more from them in the end as I didn't want a third refurb....just the setup/breakdown times and shipping times were annoying enough even though I still had a backup avr to use. Understanding their terms of sale are key in dealing with A4L:
https://www.accessories4less.com/make-a-store/cms/terms/terms-and-conditions/1.html and in my case they even went a few days beyond their terms on the second bad one, so props to them. I still buy from them, I'm just not as impressed with the facility supposedly checking them out (and fwiw my understanding is the majority of refurbs are simply returned units and not necessarily with issues).