If your setting the crossover on your Amp/AVR, then you want to turn the crossover setting on the Sub all the way clockwise to get it out of the way, and let the receiver manage the crossover. I would say use 80 on the Amp, that is a good rule of thumb and follows THX standards.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85