Dear @golfnutz : 1+ .
Two subs are enough to listen MUSIC at one seat position, the key is " one seat position ". Normally to listen MUSIC we all need only one seat position that's normally is the best position not only for the bass range but for the mid and high frequency ranges. We have to take care what is happening at that seat position because is the one we use to listen MUSIC in a stereo way.
R.