I'm always tweaking my system for the flattest response possible, but occasionally like to boost the bass a little bit. I don't think anyone who's been over to my place would say I'm not a bass head, however, if you seriously need 19 db of boost then you clearly are a basshead and clearly don't desire a flat response. At 0 that should give you 10 ticks of boost, but only -1 in case of any changes. Any placement change of your main speakers/subwoofer or addition of subwoofers means that you have to start to play with subwoofer gains in addition to Audyssey settings. Staying around 0 still gives you +10 and -10, but starting at -9 seriously hamstrings you. I'm at a loss for what you'd be listening to at -9 and then need an adjustment all the way up to +10. It just doesn't make sense to me, but as long as it does and it works for you, power to you. It's just not something I would ever recommend because I don't see what there is to gain from it. However, if it makes sense to whomever is adjusting their own system, then I guess it works for them/you.