When we moved into our present place, I bought an APC UPS / power conditioner for designed for AV needs. It was one of the best things I did for improving both the sound through the stereo and picture quality of the TV. Picture quality was one thing, but the improvement in the sound was stunning.
Here is an intriguing product that is starting to get people to convert off some pretty serious and expensive power generation stations. I will be watching this technology closely and if I find one on the used market may snap it up.
PS Audio makes one as well.