There has been much talk about listener 'fatigue' being caused by, among other things - many of which have been pointed out above, excessive RFI/EMI interference riding on top of the music. I'm not an expert on the topic, but I understand that CD players are especially problematic in this area and can be tweaked and modified to good effect. Power line conditioning that is synergistic with your system and listening tastes may be a point to consider as well. I have personally been rather intrigued by this topic and have just been getting around to tweaking on this level. I have picked up a pair of Walker High Definition Links which are specifically aimed at RFI reduction and they have had a very interesting effect on my system; a subtle yet pervasive enhancement that has me thinking about what to do next.
