I actually A/B'd the 2400 against the 2805 at my local Tweeter using Polk RTI's. They are similarly priced (the 3805 is $300 more).
I thought the Yammi was fairly neutral and the Dennon was slightly warmer and had more bass punch when listening to the audio CD's I brought along.
I also brought my LOTR Return of the King DVD with me, and could not tell the two receivers apart.
That said, I think that if you are using it mostly for home theater, the Yamaha would be a good choice, since it has better DSP's, but I would recommend the Dennon if you mostly listen to music.
It was a difficult choice for me, but I chose the Dennon.