I may just try one of the cheaper units from APC for now (since i can always return it) and report back here as to how it worked out for me.You may just damage your audio equipment......
Before you hook the cheapo UPS battery back up unit to your audio equipment I suggest you take it to your technician and have him do a bench test with a scope hooked up to the load side of it. Use a 150 watt light bulb for the load.
After everything is set up and the light is lit unplug the UPS from the wall AC power..... More than likely you will see the light flicker and get brighter for a split second. Then take a look at the sine wave on the scope..... That square wave could damage the power supply/s in your audio equipment.