Power Conditioner vs A/C cables

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.

At a certain point in developing your system it ceases to be about what is 'necessary'.

I am a firm believer in the importance of the quality of the power that feeds our components - we start with an extremely small signal and amplify it using that power, so it could be argued that we are listening to that power supply. That's aside from noise and the environment issues in the air and from other components on the same circuit, which includes all the crap wall warts that power items that are not part of our system. Everything on a circuit forms part of that circuit.

I use an Ansuz Mainz8 C2 distributor and the difference it made to the sound quality was significant. I use matching power cables to the distributor from the wall and to my speakers (active, so I am talking about power cables to the amplification).

I will get another power cable for the wall to distributor connection (tempted to try Sablon Audio as I'd like to use a D2 to the distributor but that's a price that I'm not quite comfortable with) and then use the existing C2 power cable for my DAC. The DAVE seems quite sensitive to power quality and using a decent power cable to it provided a noticeable improvement. Or I might get a Sean Jacobs DC4 instead. I was quite surprised at the difference the power cable made to the DAVE. It seemed to make no difference to my streamer though, so I'll leave that with a standard power cable.

In my experience, quality power is the foundation of getting the best possible sound from your system.

But, to answer your question... no, it's not 'necessary'.