Check the fuses.
Sholling is right. If you have a warranty on it, it's absolutely worth it to get it fixed or exchange it for the very same model or the 906.
Just use your older receiver for now, while you're dealing with your 876.
Don't even think to add an Emotiva amp to a broken 876. Get it fixed or replaced. It can be a simple thing as a burn fuse. I will check on that first.
Very easy: remove the top cover, and look near the back on the right wall (when facing your receiver from the rear), you'll see 4 fuses there, I believe, with white type of coloring. You'll have to remove them to test them.
If you don't know how, just bring them to an audio dealer close to you.
So, try that first and see how it goes.
And let us know.
But besides anything, your 876 is a great receiver worthy of anything.
Bob