I would say it would depend on how bad the power is in your house. I am going to assume most modern electronics have voltage regulators built into them. Not to mention they convert ac to dc to run. AC from your wall is normally going to fluctuate. I have seen mine go up and down from like 108 to 130 at times. Its normally around 124 I think? It doesn't effect how my tv works, my amp doesn't get softer or louder and disks don't spin faster or slower. I doubt they are doing anything that you will hear. If anything it is an added measure of protection for your equipment. I personally use a couple of UPS's for my system since my computer is part of it. We used to have problems with out power cycling on and off randomly sometimes. Which would cause stuff turn on and off three or four times quickly. That can't be good on stuff. And also if the power does go out it gives me time to shut everything down properly.
Surge protectors help with power spikes but I wouldn't count on one to save you if you get a direct lightning strike to your house. I had a tree in my front yard get hit by lightning once years ago. Some stuff was fine, other stuff was ruined. It was completely random. My AVR and dvd player were fine, but smoke was coming out of my tv. And I lost a blender in the kitchen. It also broke a window and destroyed the tree. Didn't help my relationship any either. My wife ran for the kids, I ran to the tv lol.
