gdhal, you have been told the truth ... nothing will protect you from a direct hit except unplugging ... talk to people who have had every electric device in their home fried, no matter on or off ... I once saw a service panel blown off a concrete wall and 20 feet across the room, straight through a steel-clad door; sure darn glad I wasn't there to see it ...
I can't think of any scenario where the supply AC would impact the signal path through an audio device. Capacitors were "invented" a long, long time ago, and so were AC -> DC circuits. I suppose if you really tried, you might find a real junk piece of equipment where the sound is changed as a result of wild changes to the AC or environmental RFI, but that's a stretch.
That said, I do have my important entertainment stuff (including TV and cable box DVR) plugged into high quality computer surge protectors with battery backup. Why? Because they might be effective (and supposedly insured to $1 million) if something truly awful happens on the AC side. Also, when the power goes out for 5-10 seconds, the equipment doesn't switch off and on, which I think must be hard on it after a while. When the DVR loses power, it takes 20 minutes to reboot, which is REALLY annoying. Separately, my Rowland pre's run through their own battery backed power supply, which is good because when the pre's truly lose power (such as when you unplug them from that power supply) they instantly forget every single stinking setting, including the phono pre settings. I think Rowland did the battery power supply "feature" mostly to avoid angry late night phone calls.
As always, your mileage may vary
