In my opinion, there may or may not be any point chasing higher SINAD that is higher than a certain point, and that's why a few years ago, I would not have suggested anyone to choose something like a Marantz SR7012 or 7013 over the Den...
The last sale on eBay was for $4400 + $200 shipping. That unit had some damage to the case. Two others sold for $4950 and $4915 but those listings are no longer searchable on eBay. Interestingly the original service manual recently sold for $95 itself. I would guess a reasonable price...