If you follow the pamphlet that came with your sub, it states to start "midway of 9 o'clock", which is about 6-7 o'clock, very low. Keep in mind, no matter what setting you have this volume knob at, your still getting ALL 500 watts of power. When you calibrate your speakers, you will then adjust the sub dB's on the receiver to get your desired SPL reading, usually 75dB.
With my EP600 around 6-7 o'clock, my Denon AVR has my sub level at 0dB, a very good position.
Crossover on bypass, since your using your AVR to control the crossover.
Trim on Flat for most situations, however, your room may do better on Half or Full.
