OK, let's start @ the beginning. What size 12 volts inputs do you have? Ground and positive. Are you using a clean ground? Have you got a stock electrical system (I'm going to assume yes). You need to upgrade the BIG 3. Do a search on that. Basically, it sounds like you are not getting enough voltage to your amp. Don't worry about setting gains right now, that is probably not the issue. Get the BIG 3 done, and make sure all wiring is tight, and your ground is less than 12 inches long, with solid metal scraped back until it is shiny. It sounds like you are starving your amp electrically, and it is throwing direct current out to your woofers. Don't play it too much like this, you will kill them and the amp.