I wonder if selling your S975 and trading up to an SX900 would cost as much as the Zoom processors?

The SX900 has EIGHT freely assignable insert multi-effects in addition to the usual global send effects...

You wouldn't have to go through all the faff of assigning sounds to auxiliary outs and storing that in the Registration, then all the cabling to send to the external multi-effect and then on to the mixer, in addition to the faff of having somehow to either hand select the algorithm you need or embed PC changes into the style or sequence to call them up in the Zoom. Not to mention zero ability to adjust them from the arranger's screen.

Maybe it's time to migrate, while the 975 still has decent value?