I have an SMS-1 with FOUR subs and as along as everything is balanced(volume) and in phase it does the job well. One thing, however, I have found over the years, is that with any of these EQ devices and regardless of how many positions from which the calibration can be done, one can come up with a level, balanced curve showing on the screen yet it may still not sound quite right and that is generally as a result of the limitations of human hearing.
For eg: a couple of years back when I purchased the SMS-1 and in doing my initial calibration, I noticed a distinct deficiency in my room with the curve between 40-55HZ. Once I got it leveled out, however, I noticed that even though it was showing a proper balance, the lower levels below 40HZ(at least to my ears anyway) were being overpowered by the upper levels, and that was despite the fact it was showing a level curve on the screen.
In my opinion, this is the advantage of having one of these units in that it allowed me to slightly boost up those lower levels to compensate for what I was hearing in relation to the "official" calibrated curve. That is, of course, provided your subs can handle that "extra boost".
In the end, it is what sounds good to you that will determine what your final set-up is, but given the "finnicky" nature of low bass in any room, either the SMS-1 or EQ-1 will give you a better chance of getting where you want to go.
