I can only pass this along: I heard once that UPS' give an AC waveform that looks more like a square wave rather than the sine wave that you get out of the wall. Because of that, there was some comment about how that might not be good for an electrical component's performance. But, I have also heard similarly, other's using UPS' for the same function as yourself. If it does work OK, I would make sure that the UPS is "powerful" enough or of large enough capacity that you aren't limiting the power to your system for the transients present in movies, music, etc.

Maybe just like surge suppressors, there are "good" ones and "bad" ones.

Maybe SH, BoB, Charlie, etc, can chime in...