If you are buying new, no way unless you go to Denon's website and confirm the reseller is an official partner and can offer a warranty.
Refurbished, there is at least one reseller on eBay that is selling manufactured refurbished receivers that do come with a warranty. However, you can get the same price (sometimes better) off their website.
Used, as long as you know it's a bit of a gamble, why not. I have purchased a used Denon off eBay. It didn't work out for me, but it was worth a shot. No regrets.
Is it solipsistic in here, or is it just me?