Here is what the manual says about the crossover on my HU.
WOOFER Subwoofer cutoff frequency
LOW: Frequencies lower than 55 Hz are send to the subwoofer.
MID: [Initial]; Frequencies lower than 85 Hz are send to the subwoofer.
HIGH: Frequencies lower than 115 Hz are send to the subwoofer.
Now it is set to mid. Should I raise it up to high, or is 85Hz enough for the subs? And if I have this set do I need the crossover on the amp? I don't think I can turn off this crossover.