Ideally, you should start by setting your preamp volume control to "0" or "ref", and all the individual channel trims to zero. Play a DVD with test pink noise (5.1). Set the gain pot on the power amps for 75db sound pressure level per speaker. I know this sounds counter-intuitive, but that is the way it is done on film dubbing stages, except the reference level is 85db instead of 75db. Doing this, besides giving you a calibrated reference setting on your volume control, insures the best gain structure for the reproduction chain. I know, I know, this is not how it is presented in most consumer manuals, but just trust me on this one.