So, my main fronts (mission 782's) have a bottom end of 48hz, my rear surrounds (780's) have a bottom end of 65hz, and my centre (78c) has a bottom end of 75hz. Is a good place to start tweaking my sub (78as) at 50hz? Or should I set it a bit higher, say 65-70 so the sub can pick up the bass for the mains and the rears too? Or should I go higher, 75ish so it deals with the stuff the centre can't hack? I am currently experimenting by setting my av amp speaker settings to "small" for the fronts, rears, and centre channels, thus forcing all the bass (I don't know and can't find anywhere the crossover setting of my amp nad 753 if you happen to know it) to the sub, yes? As for positioning, that I can do last, yes, no?