Most Beneficial Cable Upgrade

I expect delivery of some new equipment tomorrow. My dealer promised to bring some high end power cables to audiition.
I have all high end equipment, including speaker cables and interconnects. All of my amps (All Krell evo e series for home theater and stereo music) are on seperate dedicated 115 amp lines. I never bothered upgrading my stock power cables, and I have never compared power cables, it has simply not been a priority for me. However, I am curious to see if changing power cables will make an audible improvement (to my ears). My plan is very simple, I will try differenct cables, short term and long term (a few days). I will try some blind and nonblind switching (with help from my wife). That is the best I can do. I have no recording equipment, so I will not do anything elaborate with reordings as mentioned above. I doubt recording with a microphpone would help since recording in this manner will add conditions which will affect sound.
I must admit, I do have a pre-audition opinion. I have been buying high end audio equipment since the early 1970's. Some changes are exremely subtle, some are very dramatic and rewarding. I think the change will be so subtle that I will have to really strain to identify the improvment. This would leave me uncertain (which I consider inconsequential). I will upgrade if I can detect an improvement. I hope it does make my equipment sound better. Like everyone else here on Audiogon, I am constantly looking for ways to improve the sound of my equipment. I will approach this with an open mind. We have had a very mixed response on this thread. Some people feel very strongly that power cables make an obvious improvement, others think it makes no difference. For me, this is all fun. The audition may take me a couple of weeks. I will let you know.

I do agree that the standard electrical outlets in most homes should be replaced; weak grip, thin contact material, cost the builder maybe $1 per duplex plug. Changing them to a higher quality plug is worthwhile and relatively easy if you are knowledgeable about electricity, circuit breakers and tools, cost me $7 per plug to replace with 20 amp heavy duty plugs. You can also buy the $50 cryo treated ones but that means 2 less (SA)CD's in your collection ( per). Interfaces are where most signal degradation/interference occurs.

I borrowed several simple devices, which measure noise on an AC conduit. One was Monster Power "Dr. Power" and the other was AudioPrism "Noise Sniffer". The devices seem gimicky but yield startling noises.

During the test, I unplugged the ice machine and two refrigerators. The noise was substatially reduced. I still heard static, motor whining and switching clicks. I unplugged the back-up UPS in my office and the static disapeared.

I went outside and heard my neighbor's swimming pool pump running. When the pump switched-off, I ran inside and noticed the motor noise had disappeared. I never found a local source for the clicking but suspect an old capacitor bank on the utility pole about 1/2 mile from my home.

Later that month, I purchased a used Monster Power "Monster Pro 2500" power conditioner for $100. I plugged both noise devices into the Pro 2500 and there was silence (even with the ice machine and refrigerators cycling).

I was amazed how much noise regular household devices were feeding-back onto my Stereo-dedicated AC conduit. Hair dryer, clothes washing machine, central air handler, central vacuum, VCR, food blender, bathroom exhaust fan and microwave ovens were offenders.

Now, I am ready to experiment with special power cords.

Bruce,
I agree about the noise problem in electrical line. This is one advantage of dedicated lines for power amps. It eliminates noise and draw from household electronic appliances. It provides cleaner power and more stable power.

Need to carry that thought a little further. A dedicated line doesn't provide that much additional isolation if on the same phase circuit as all other circuits in the house... all of those circuits are connected in parallel at the breaker junction. To get better physical isolation your dedicated circuit needs to be on the phase connection with least amount of other disruptive devices. Most houses are at least 2 phase (220 volts) and if you have a monster power need you might be 3 phase. Most junction boxes take the easy approach of loading up all their single phase circuits on 1 phase tap. Can't say that i've played with this but you can likely run from the second phase tap for a single phase circuit