That would be my worry. How much current are you talking about? Could you use a real computer grade AVR? We have some in our server rack that are 6000 watt and they surely do make smaller ones.
That doesn't worry me in this particular situation. They've got a Monster power conditioner as the distro in the rack, and it's got a BIG voltage display they watch all the time. But even if somehow the incoming voltage goes up to 120, then my 6 volt boost would only take it 126 which should be perfectly safe for everything. Hey, the line voltage at my school is 130, which made me a little worried the first time we measured it in sound practicum class, but the school plant guys insists it's been like that for a decade. What is it with these plant guys?
Right now, the church sound tech manually cycles the HVAC units off when the voltage gets below 110 and the preacher is doing his message. Then they'll turn the HVAC compressors back on when the choir and band is singing and let the voltage drop below 110 since the congregation can't hear the buzz from the monitors. Now these are BIG compressors since the room seats at least 2,000, but they have a wall mounted control next to the monitor console so at least he doesn't have to run into an equipment closest to tweak the HVAC.
If this cheap fix works, then I've suggested they use it as a pitch to PoCo to fix the incoming voltage sag, but their plant guy insists the PoCo says they're not responsible for fixing the street transformers since the church is in an industrial park. Don't know what that has to do with it, but sounds to me like PoCo is just knitting A$$hole covers.