If you have a spare slot then clearing the filters for that slot doesn't make a difference. You can run a combination of basic and advanced filters in one configuration.
I would start with 6dB and run some tests, yes. If that's not enough and you have the headroom then it's ok to add more, just be cautious. Do you always listen at about the same level? If that level changes significantly, say between movies and TV, then you might want multiple profiles. The louder you listen the less house curve you need.
I would start with 6dB and run some tests, yes. If that's not enough and you have the headroom then it's ok to add more, just be cautious. Do you always listen at about the same level? If that level changes significantly, say between movies and TV, then you might want multiple profiles. The louder you listen the less house curve you need.