You can now purchase Denon products directly from Denon in the US at http://usa.denon.com/
Why would you want to purchase direclty from Denon?
Pricing - Nope. Denon controls their pricing and you have to pay the same price from all authorized dealers, the price on their website is List Price. Same as what you'll pay everywhere else.
Shipping - For the moment they are offering free shipping but you have to enter the promo code Welcome
Perks - Right now they are sending free hats with every purchase. OK, cool, but not a reason to buy from them.
Bottom line - Buying from the manufacturer direct is a good deal IF they offer the same support as a dealer. You will need to pay tax if you are in NJ, NY, CA or IN Since Denon has offices in those states.
Denon is not known for great customer support so you have to consider this when purchasing. On the other hand they need this to succeed so you might have leverage you won't have at other online stores.
Buy from Amazon - You can of course get the free shipping, no tax and the full support of purchase from Amazon. At least with Amazon you'll know for sure that issues and returns will be handled quickly and without problems.