I just purchase a Panasonic CQ-DF601U Head unit with a Subwoofer Preamp output, When i connect my RCA cable to the preamp output, and the head unit says you can set it to 80hz or 120hz, also has a bass gain from 0-8. Right now my thing is set to 80hz and the bass gain is 3. What should i set it on, 80hz right and whatever depends on the bass gain i feel like setting? Also if its on 80hz on my head unit, do i have to go to my amp crossover to put it on 0hz? Right now my amp crossover is on 80hz. Any suggestions what i should do? Hopefully you understand what i'm saying. Thanks!