I went through the exact same thing "Denon 2808CI or Onkyo SR875. Also keep in mind that I was upgrading from an older Denon model. After all the research they both have all the features and many more that you would need in almost any application. However if you look closer at the video portion IMOP the Onkyo comes out on top. I was unsure of the power output that Onkyo claimes to have per channel. And of course all us Denon owners know that what Denon states is always right on! I was stuck but do to the fact of the better video quality (HQV) I went with the Onkyo. I could not be happier. The 1080p upscaling is awesome. I have an older DVD player hooked up and it is amazing what the HQV can do to just a regular DVD. The HD-blu-ray is very impressive. Now not owning the Denon I cant say how well the upscaling is but if you are in doubt of the performace of the Onkyo I can personnaly tell you that it has performed well over my expectations. The setup on the 7.1 is also very cool. You just put the mic in your listening postions and run the built in program and your done. Of course you will want to do some minor tweeks but it gets you going in the right direction.
Hope this helps in you decision.
