If your concern is still the failures of the 975 due to low voltage conditions get a sufficiently rated UPS and just power the 975 from it. Most UPS' have some sort of indication on them when they are providing power. Monitor that function to determine if the 975 is being challenged. I have two 20 amp circuits in my audio room one for the music system and the other for the HT system and I don't have nearly the amp draw that you have. Remember too that the lowest voltage you see may not be the lowest voltage attained due to the limitations of the meters reading fast transients.