Breathe easy. The perfect sine wave with no THD is mostly myth. All power supplies in modern electronics are tanking supplies. They rectify the AC into DC to charge a capacitor, then tap the capacitor to provide the necessary voltages. They run just fine off of a square wave. Take a look at the wave output of an APC uninterruptible power supply sometime. It's a modified square wave, but runs computers, satellite dishes and TVs just fine. Just don't try to plug an old AM radio into it, because all you will hear is static. Most surge protectors have a built in RF choke to reduce the amount of radio frequencies, so plug one in if you need to. The only problem I ever had with an APC unit was the digital clock on a satellite receiver going wonky and screwing up the DVR timing, but as soon as power returned it was fine.