+1 on the system cleanse benefits the Isotek disc performs on my systems.
While we are talking about it demagnetizing CDs impacts a noticable improvement to the sound quality as well.
If you have a CD Player, you need to do this periodically...
I would rather imagine that most audiophiles are aware of this, but if not, may I recommend a very easy tweak that has always produced positive results in every system I've had:
Ayre - Irrational, But Efficacious!
Densen - DeMagic
These are System Enhancement Discs which reduces magnetism that has built up during playback. I'm pretty sure there are other products that purport to do the same thing. These two have certainly worked for me. Good listening!!