In my case, fronts are large, center is good down to 50Hz and sides/rears good to 80Hz.

How much difference does setting the crossover at 80Hz versus 50Hz really make?

I have noticed that all modes for music, except for direct, send some signal to the sub (even stereo with the front L+R set to large), so the bass rollover to sub in these modes is based on something other than the crossover setting.

861v6, Oppo83 (3xSpdif Mod), Wiim Ultra running Squeezelite, Tivo Edge, Apple TV v4 with Key Digtial Audio Extractor, Von Schweikert fronts and center, Triad in ceiling sides and rears, Aerial SW12, Orchard Audio Starkrimson 3 channel and Sunfire Cinema Grand amps