hmm its interesting to note that a linear power supply has a big transformer, read inductor in it, this theoretically should act as a filter in itself for mains crap, add to this, the design of circuits following op-amps lead for low power supply susceptibility...and regulators which further reduce psu variations,
and for a while I was rather anti any superfluous extraneous conditioners a la RA psuedoscientific bullshit, for the above reasons, however, the fact that systems sound different at different times, and other bits does lead me to believe that these external bits by respectable companies such as trichord or the pro audio people who make the trichord...have a look in sound on sound magazine for the same model, different name,could be well useful.