There is another issue here. We are now past the point where RCA video outputs are no longer legal. Digital AV units are only allowed to have digital outputs that conform to current DRM rules. Whist the analog 5.1 inputs might be legal, current equipment does not have 5.1 or more RCA outputs, so there is really no point in putting them on the AVRs or AVPs. as only legacy equipment could use it. I am not even certain those 5.1 audio inputs are even legal any longer.
There is an absolute forcing of HDMI in AV equipment now. All the gear does contain analog left and right RCA inputs I think for stereo analog units, and that is all you need, and I have a feeling those are the only ones that are legal.