Hi warl.
IMHO, you should take the Sony off the list. Their products don't start get getting good until up in the higher priced "E" series.
You can't go wrong with either Onk or Denon. The Denon's are difficult to set up - crummy Manuals. But, many people prefer the Denon sound over the Onk - especially in stereo music playback. Not to say that the Onks sound bad, they don't. I have an 805.
I recommend that , if possible, you auditon the Denon and the Onk w/ the same speakers. Oh . . . for comparison, do try the Yamahas and Pioneers in this price range. Performance and feature wise, all of these brands are recommended. But, to many people, they sound different. So many choices.

Have fun shopping.

Mike