If I'm right that the receiver has a fixed crossover at 80 Hz, then what you said is correct.
If you are using the crossover in the receiver, it's usually best to not use the crossover in the sub (just like your subwoofer manual states). Some subs will let you bypass the crossover. With subs that don't have a bypass, you'd just set the crossover frequency on the sub to the highest possible setting.