Puerto - What specifically are you concerned about for your equipment? The APC S15 is, in a sense, performing a voltage regulation function because it isn't allowing voltages outside of a certain range to reach your equipment. It almost sounds like you're looking for something that will avoid "sounding the alarm" more than you're in need of better protection.
I'm almost thinking that a power regenerator might be what you're looking for, but not sure how they would perform under the power conditions you describe.
I'm almost thinking that a power regenerator might be what you're looking for, but not sure how they would perform under the power conditions you describe.