Do isolation devices really help?

I am curious about your thoughts on isolation devices--cones, pads, etc.. Do they really help? I can maybe understand how they may help with a CD player because you have a rotating disc moving picking up signals. But for solid state equipment like the preamp and amp I really don't understand what they would contribute for improving sound quality. I'm thinking about cones, etc for my CD transport. Any advice and comments about effect on other components?