Any sine wave inverter of good quality will work. BUT... Are you trying to have backup (battery) power as well, or just a filter for dirty electricity? An inverter, technically, is changing DC power to AC, and can also improve the "quality" of the electricity as it does so. I'm guessing what you really want is an Uninterruptable Power Supply, as most utillity power in the US is about as good as it gets. If it is a UPS you want, a high quality APC unit may do the trick, but capability (and thus quality, for what you want) can vary greatly even within that brand. Look for one that produces a pures sine wave, as noted, and that has both "trim" and "boost" functions, which keeps voltage steady. Finally, if you will ever run on generator make sure to test it immediately on gen power (and make sure it is returnable), as many UPS will not operate properly on gen power, something you don't want to find out in a power outage.