Power Conditioner vs A/C cables

note on some comments above.  IMO the gold standard for a real, practical power conditioner is an industrial isolation transformer.  if oyu get one in the 2 kilowatt range, it will deliver plenty of transient power capability, will eliminate and DC component, filter out HF noise and reduce/eliminate ground noise.  Yes some series filtering is also helpful - i do it.
I would in fact argue against buying these form high end firms and get ones that meet medical requirements.  Just like I did.  The put another filter between your analog components and the dirty switch mode power supply stuff, bane of our AC lives.  Thes put noise "backward"to the grid and the rest of your house.

You need both you will be amazed when you get the match right to each component in your system it is like buying a whole new system.

I use AC regenerator and aftermarket cables from a guy on this site (acoustic bbq) and both made a difference. The regenerator made an enormous difference though.

I would in fact argue against buying these form high end firms and get ones that meet medical requirements.

I fully agree. As far as I'm concerned audio equipment is just as sensitive as medical equipment, yet few seem to understand the impact and even fewer manufacturers comprehend how easily a quality sound can be degraded by emissions from internal power supplies. It is crucial internal power supply and rectifiers are shielded from other circuitry or even better housed in external cases.

Since few manufactures provide power supplies in external cases, I take a peek inside and consider how and where I can add shielding with a grounding wire. I've done all my equipment and the results are simply stunning. Perhaps I should say it is shocking I have been able to make such amazing improvements that were overlooked/ignored by manufacturers.

Some even go so far as to put dummy plugs in unused ports to eliminate the possibility of proving a direct antenna path to circuitry.

Which I have done, and also gone one step further by putting a stainless-steel gauze used for protection against high frequency radiation and low frequency electric fields over ventilation holes. The one I used is made of thin wire that makes very little impact to air flow.

While phono levels are the most sensitive to contamination, so too are CD/Blu-ray readers, and indeed everything all the way up to and including speaker cables. Yeah, I know you're going to add capacitance, but I believe the benefit absolutely outweighs any negative, particularly when you use quality speaker cable and keep the two wires separated rather than encased.

A question. Some big IBM mainframes used motor generators to create juice of different voltage, phase and frequency. 
Why not an audio motor generator? All it has to do is create clean 60 Hz, 120+- volts, single phase power. All audio units would be plugged into the generator. The juice would be isolated from vagaries and noise of the electric companies juice. A flywheel would keep the output good if the input faltered a bit. The unit could be fed by a decent UPS for when the grid goes away. Don’t worry about lightning strikes. Any network connection would go through an optical coupler.

True isolated power.