Ok, after some uncorrected measurements of my subwoofers, both the 2 RSLs and the 1 Hsu, I'm sticking to the 2 RSLs and will return the Hsu.
I messed around with positioning the RSLs in the positions where it would still be aesthetically pleasing and not in the way (again, this is the main living room so I can't just place them anywhere for the sake of the best sound, it's a compromise), while providing the flattest measurement. In some cases I had to move my left sub an inch closer to a wall to get rid of a major null.
And then finally, I made corrections with MultEQ-X and with Dirac Live Bass Control. Full range measurements below (no smoothing applied so you can see the lower frequencies as well):
Audyssey Reference (High Frequency Roll-off, no added boosting anywhere, front R+L crossed at 150hz):
Audyssey Flat (no corrections above 250hz, tilt applied where it rises to +3dB by 50hz from higher frequencies):
Dirac Full Range (no low-end boost, front R+L crossed at 150hz):
Dirac 250hz curtain (no corrections above 250hz, no low-end boost, front R+L crossed at 150hz):
Measurement wise, Audyssey Reference gives the best result. There are some room modes that can't be corrected, probably only addressable with room treatments which I don't plan on doing in this place (it's just a rental for the next year or so). MultEQ-X is a great little tool that allows for some additional tweaking (though too bad it's only available for Windows and not on Mac, but I have both systems so not a huge deal in the end).
So, I will likely request a Dirac refund here soon.
Any other REW graphs I should post to show a comparison between these corrections?
Otherwise I'm done messing with this system and will not touch it again until I move to a different house.