Even if you have a top notch utility and a perfect house the power system is still grounded to the earth. When lightning strikes the ground close to your home, that ground path can go right to the third prong on a grounded system and to one of the other prongs on the two prong systems. I have not seen any evidence from a reviewer that definitively shows an improvement in either sound quality or video quality when using a power conditioner. I also avoid all the snake oil sales pitches out there but still have my equipment protected the best I can afford.