Excellent way to save some money or push your budget for a superior product. Half my systems are either refurbs, reconditioned or used and have had very good luck with them.
eCost is one location to look for refurbished Denon or Onkyo receivers, AC4Less is also another good place as DavidTwoTrees mentioned above. Dakmart is also another reputable location to find refurbished Denon receivers as well.
There is a bit of risk going with a refurb, but if the seller is reputable and it comes with a valid manufacturer's warranty, albeit limited compared to new, the reward is there as well... -TD