first, no no no bass boost. second, you only need subsonic filter if the subs are in a ported box, most say 5-10hrtz below box tuning. the best way to set gains is with a dmm, to set by ear; turn the gain on amp to it's lowest setting, no boosted signal at all, turn the bass setting on hu to zero. turn head unit volume up until it starts to sound distorted then backdown until clear, usually about 85% of max volume. turn the gain up on the amp, again stop when the signal sounds distorted, and back it down a bit. not the best way, but will work most of the time. set the low pass filter usually between 80-100hrtz. phase at zero unless subs are inverted. also, no bass boost on hu, if there are controls for the sub, you can use that. my kenwood x396's sub control is 0-15, i have it on 15. like i said, not the best way, but will work.