I picked up an APC SmartUPS off eBay, minus the batteries, for $80. Generic batteries set me back another $20 or so. I like it, it works, and it's quieter than my PC

if there is a reasonable load on it, it's practically silent.
It also does voltage regulation, but the switching isn't as quiet as my Furman AR1215. However the voltage at my house is very stable, so no worries there.