start at .1v, and turn up the gain until you hear distortion, then turn it back down. I have the same set up as you( except I have one type R), and i have my gain turned all the way down to.1v because it sounds best like that. I dont think you will even have to screw around with the gain much man to make those subs pound. You are right the lower the gain is the higher the gain is turned up. 2v is a higher setting than 4v as far as gains go. Let me know how your system sounds man, because mine hits insanely with just one type R man, thinking about another. peace.