What I have setup now---
1. Low pass set to LPF (sub says to set it here when using LFE out from AVR)
2. Phase control set to "0"
3. sub volume around 60%
4. Using sub cable from LFE in to AVR
1. Sub mode on
2. All speakers set to small
3. Speaker crossovers set to 80Hz
There is no low pass filter setting in the Pio unfortunately. Should I keep it this way or set it up to have the sub's low pass knob on 120Hz and not let AVR process it?
The crossover frequency you select in the AVR sets the HPF for all "Small" speaker and LPF for the sub. So, while there isn't a separate LPF setting for the sub, the receiver is applying 80Hz LPF to the sub.
Generally speaking, the sub/AVR connection and LPF/crossover settings seem correct to me.
Just because there is a knob doesn't mean you should turn it.