The Onkyo 876 you were considering will beat all everything that has been montioned here without even flinching...and this is coming from a Denon fanboy. However you will have to find it refurbished to meet your price point...I know accessories4less.com has them and they are factory certified w/warranty....
The Onkyo's provide the most power and processing for the $$$...I know last time I looked they had factory certified TX-NR905's for $899....If you could swing that you would have a beast of an AVR....just be careful as the Onkyo's need proper ventilation as they run hot....
If not the Onkyo then the next pick would be the Denon for sure...
I've had Onkyo before. They are good receivers, but they run pretty hot. They also are so so when it comes to sound quality. When I switched from an $800 Onkyo receiver to my Rotel that granted was a few hundred more, the SQ difference was night and day..
I haven't heard the new Marantz, but I had a high line and I mean high line AV shop owner recommend them very highly.
I decided to go with an Arcam, but the reviews on the Marantz's have been very impressive.
Don't get me wrong though. Onkyo does make a good product. My old receiver is still running at my Ex-wife's home and it has been trouble free for almost 10 years...