I have a yamaha receiver amd almost always have it set to straight. I upgraded to windows 8.1 from 8. Before the upgrade stereo would show 2 channel and maybe the sub too on the little display for what speakers are showing inputs. After the upgrade, the receiver always displays 5.1 channel. Amazon prime sounds like upmixed stereo. My surrounds have dialog and all. Playing music from media monkey shows 5.1, but the sound is only coming out in stereo. Anyone else experiencing anything like this after the upgrade? What gives?