I leave my settings alone. I also use a SMS-1, so I can adjust the subwoofer's volume on-the-fly if I want to, but I rarely do.
My Outlaw 990 is set to defaul to -25db and the highest I go is -5db. The bass seems to perform well enough for me at the current settings without having to tweak as I get louder, I usually do not run my system at less than -25db volume.