Re: RX-V861 dead center channel
Have you tried auto setup with the supplied microphone? If not, have you checked your speaker level adjustment (see page 48 of user's manual for process). The center may be turned all the way down.
Connect the subwoofer to the subwoofer pre-out using a quality subwoofer cable. Play a 5.1 source through the amp and you should see the LFE indicator illuminated on the receiver's display.
I am trying not to make any assumptions. Setting the speakers to small or large will not turn off output to the center channel speaker.
Let me know if you have success. Good luck.