This really is a cool deal. You've got a way to document frequency response in the space, and the result is a discovery that all your work with sub placement and acoustical treatment (and your trio of subwoofers) has achieved an ideal condition: flat response across the subs' range. As much as I've enjoyed tinkering with my SMS-1 to address an array of mild but noticeable dips and peaks (noticeable once removed, at least), this seems like a case where the SMS-1's tricks aren't required. Definitely a strong case for room treatment, optimized sub placement, and the "smoothing-out" benefits of multiple subs.

Yep - the default slider positions are all below 100Hz, and the auto EQ processes don't adjust the sliders' frequency settings. Of course, you can manually move them up and down at your discretion. If I remember correctly, they can go up to 120Hz.