My Cheezewoofer Wattless subs (four now) are lazily stacked next to my mains and duplicate the low end, so no separating the 12" sealed in the speakers with the 15" ported subs.
90dB main, add first sub and adjust to 93dB, then add the second sub and adjust it to obtain 94.7dB at the listening position.
The mains are too much in the bass in this room by themselves, even with the -4dB cut on the speaker applied, so room correction cuts the trio even more on each side.
The result is lowered distortion in the bottom, 2% or less measured in a sweep, except around 50Hz where I have a room phase anomaly.
I've considered separating things with another miniDSP, maybe next year (it isn't far away today), but am pleased enough with the result right now.
Bass is distinct as to simultaneous bass sources - string bass, bass guitar, low drums, wel differentiated.
I'm not a head banger - 105dBZ peaks are generally enough. 117dBz musical peak has been measured, but that was a brief episode of "too much".
I correct for flat (to the consternation of the folks with WDD*, but the result suits me and the only other person that gets into it here.
However, he has an old active crossover that he resurrected from The Shed Where the Past Is Buried and will bring it over next week for measurement and test, so, who knows what will come of that exercise. He says it is quiet, beyond that, don't know.
*WDD - Wide Dispersion Disorder