Ive owned the 605 and the 1909, along with a sony 810. Sony sounded very metallic, and I dont think its fair to compare the 605 to the 1909.
For the $600 rcvr, I decided on Denon for build quality and the better Audyssey setup. I think the more points it measure, the better.
The Denon 1909 does however have better AQ than the other two I owned.
I feel, after doing my research, if you hit the mid to upper tier rcvr's like 1909's, 3808's, 800 series Onkyos, and the more expensive Pioneers, you are getting a good receiver($600 price range in BBuy gets you a great rcvr).
I dont have any reason to think the Onkyo is less a build than the Denon, I just did not like the heat. I gotta think, less heat means more longevity because heat is bad for electronics. Whether or not it means an onkkyo would last 8 yrs as compared to a Denons 10is unknown, and prob not that big of a deal.
After owning this Denon, I can say its my fav so far, and it most likely means I wont stray from them in the future. Just like Panasonic and their BR players.