turn gain down to 1/2 what it's at and set volume to max level u listen at and adjust gain to where it sounds good, when u turn volume down to 1/2 speakers should sound good.. amp gain is for u to match the hu so u don't want it to be loud on low volume.. set the xovers as i said.. are u saying u have the 4 chanel bridged to your door speakers?, if so thats fine just turn gain down low... the boss amp omg those are crap!, set lp xover on that at 80hz set gain about same as i told u just don't go past like 60%.. that amp does about 200rms maybe we will be glad to help u find a much better amp (same for planet audio).. the sub is a single or dual 4ohm vc? if svc 4 ohm u only getting like 80 watts off that amp, u be better off with 2 channel bridged if d4 then we can should u some amps in the $100 range that'll be huge improvement..