I found the following in my manual... I do not exactly know what it means but I think this might shed some light on everyone else here who can actually interpret this!!! Please take a look
Setting the speaker impedance
Caution
If you are to use 6 ohm speakers, set “SP IMP.” to
“6Ω MIN” as follows BEFORE using this unit. 4 ohm
speakers can be also used as the front speakers.If you look on page 109 of the RX-V863 manual it says something about this that is important... I can not decipher it and I tried for a really long time to cut and paste it on here but it did not work so UGH!!!