For the past 6 years I have used my own tweaked out DIY balanced power conditioners, plugged into a dedicated 20A line. My latest implementation employs separate balanced isolation transformers for amp, preamp, and digital source. My experience has been similar to Charles1dad's, except that I would add increased low end weight and authority to the list of improvements.
http://img.villagephotos.com/p/2003-5/191557/B2_09.jpg
http://img.villagephotos.com/p/2003-5/191557/B2_08.jpg
http://img.villagephotos.com/p/2003-5/191557/b_08.jpg
http://img.villagephotos.com/p/2003-5/191557/B2_09.jpg
http://img.villagephotos.com/p/2003-5/191557/B2_08.jpg
http://img.villagephotos.com/p/2003-5/191557/b_08.jpg