The lpf should usually be somewhere around 80-100hrtz, never, EVER, use the bass boost, just adds distortion to your system. The sub sonic filter is only needed with a ported enclosure. Some will say to use either a digital multi meter-dmm, an oscili-scope, or both, to properly set your gains. Some will say to do it by ear, like some amp manuals tell you to. I have neither of these, but I also never have my gain past the half way point. My amp has an actual gain knob, with the clipping light built in. There are tutorial videos on you tube, and digital meters for pretty cheap at most auto parts stores.