Just to pitch the other side of the coin... I was listening to my stereo when a lightning storm rolled in... I saw the bolt out of two different windows that were, respectively, on the south and east sides of my house. Took out the CATV box, fried the output transistors inside a powered sub, and destroyed an ARC LS-9. I now use some power products...
My PS Audio Power Director also does improve the sound--here I have some actual objective data as well as the usual subjective "deeper blacks, etc." I used to have a pair of ARC D240s wired up (and on 24/7) to a pair of Martin Logan Prodigy speakers. The speakers had these strange blue ML logos behind the panel that glowed, and which I thought were on all the time. Well, I put in the PS Audio Power Director--which doesn't really claim to be a filter--and the lights disappeared. The speakers worked, so I went back to the manual and discovered that the lights were an indicator of a signal being present on the speaker inputs. In the absence of a signal being detected, the panels shut down.
Net takeaway... There was enough noise on my power lines to cause my speakers to think a signal was actually present. When I swapped in the PS PD, it cleaned up the lines enough that it went away. Made me a believer.
