
Pure sine, double-converted online output is the best. Enermax specifies real sine wave (not simulated sine) UPS' for their Infiniti and Galaxy PSU's and the SU-series do it well. It's quick switching to battery power when AC is down and the software works. Can accept external batteries for increased runtime. Internal heat sinks are nice - keeps things cool should you happen to use full 800 watt capacity, but most PC's never use that much even at full tilt. I have an o/c'ed E6600 & HD2900XT, 3 HDD's, 2 opticals, etc. and the output LED's haven't gone past 50%.

Purchased UPS to protect my home server (AMD FX 8320, running Windows Server 2012 R2 on Gigabyte GA-990FXA-UD3 with ~ 12 TB of parity REFS storage.) APC offers 1500VA unit at a reasonable price. Unit also provides voltage regulation and network protection. One of the nicest things about these UPSs is they are quiet. I have several units throughout my house and you may hear a “Click” when they come on but other than that they are whisper quiet.