I think you would be better off with full range speakers in a mobile setup.Yeah, I mean it's a rig I throw up in temporary working spaces so it never gets much of a chance.
But yes, different frequencies, filters, slopes, time alignment, EQing & aligning separately before or after Dirac or Trinnov, Dirac'ing the sub and main separately and combined, etc. etc.
Maybe if I tried hard enough in a permanent install I'd get there with it. But my gut feeling is, crossovers introduce problems, so I never expect to able to add another crossover to a system without it doing *something* to the sound.
Edit: but obviously as @andymarks pointed out, it's a win in other ways, so I still lug the subs around with me and go with it!
It is hard to get a sub to sound integrated. At least for me it is. Let alone 3 subs.
This my current response, sub below my desk near the front wall.
I used REW while tweaking Equalizer APO manually both speakers and sub on the same output.