You state: “The current from the power supply is what’s moving the magnets in the woofers and tweeters that creates the sound you hear.” Just to avoid confusion: this topic is about the Port, that does not drive speakers directly. If you want to try a different power supply for the Port, they are available: 

https://www.fidelityaudio.co.uk/sonos-port-pro-low-noise-psu-5089-p.asp

https://wyred4sound.com/products/digital-converters/music-servers/upgrades-accessories/sonos-port-modified

If “golden ears” are not needed, then the requested ABX test to show the electrical noise is audible to the listener should be a piece of cake.  When should I expect it?

When using the digital out, you are correct that the Port doesn’t drive the speakers directly. Nevertheless, it’s part of a network that starts with one or more power sources and ends with sound waves created by the motion of coils, magnets, ribbons or other components driven by those power sources. If the Port had an optical output that would be a different story.

If you use the variable, analog output then the Port is also both the DAC and the preamp, which are very much in the path of the current that drives the speakers. 

I agree that many audiophiles go overboard with expensive stuff, some of which may make little or no audible difference. I don’t agree that when the source is digital, nothing else matters. If you use the Port’s digital out, there’s little room to improve what comes out of the Port (perhaps none), but I wouldn’t discount the possibility of any improvement. Most of what could be improved, however, could be done at the input stage of an external DAC, e.g. re-clocking, isolation of noise so it doesn’t reach the DAC’s analog outputs, etc. 

If you’re using the Port’s DAC and preamp, that’s a whole different story.

I don’t think Sonos should make an audiophile Port. What they should make is a cheaper version of the Port that only has a digital out. Eliminating the DAC and preamp (analog in and analog out) should provide significant savings.

Not really, apart from the electrical isolation element. You might wish to acquaint yourself with digital transmission techniques. 

In percentage terms? I’d wager it would actually be a pretty small saving, considering the need for processor, memory, DSP, network interfaces, etc would be the same either way. 

A DAC chip goes for pennies, it’s a commodity product.  Even the most expensive “audiophile” DAC chips are under $10, which is a rounding error for the Port pricing. Same for the analog out. 

Thanks. I think my issue is relevant, but off topic for this thread, maybe someone could suggest another thread for using an existing 2-ch Sonos system as rear channels for a surround system without degrading the existing 2-ch system because you can only do it by putting an Amp on the 2-ch system.

The Amp replaces the external DAC, preamp and Amp on the 2-ch system. That system now has a Sub too.

That isn’t the only issue though. Switching from TV/surround to playing music on the Surround Channels through the new system is not exactly the same as playing music on the old 2-ch system. I think there is some strong DSP now on the Surround Channels. I have changed music playback from Ambient to Full and set the volume of the Surround Channels to max for Music Playback. I don’t recall if I tried turning off Trueplay, I’ll do that this weekend. If that sounds better for music I’ll just leave it off.

It’d be nice if you could set Trueplay on for TV/Surround and off for Music (or vice-versa).

Agreed. Not irrelevant, but a different story.

Not sure what DSP you have in mind, but the idea is not to mess with the source at all.

It’s all commodity stuff. I think the end product is such a stripped down version of what they put into all their products that it could be cheaper just because it’s simpler. Every little thing adds complexity. It really is the core of every Sonos product. That’s probably the main reason they won’t offer it separately.

Yes it is off topic because the only way to make a valid comparison of two alternatives is to have every other variable stay the exact same. And if you are comparing a stereo 2 channel set up with the sound from a surround set up even if the latter is on full music mode, there are far too many variables that will make a nonsense of any comparison because they will sound so different. And I can't see any way to have any existing 2 channel system set up for full time music play with front located speakers to also do rear surround - unless you are willing to give yourself the time of a few weeks to get used to how the latter sounds for music in full music mode with speakers at the rear. In that time, as it does in all cases to varying degrees, the brain will adapt itself to the new sound, and you may probably find it far more acceptable for full music listening than it does now. 

As to Port pricing it has little do with cost, but with a Sonos perceived value to users, with the price set accordingly by Sonos as a price policy. Those users that agree with that perceived value will find the present price acceptable. The same Port could be priced a lot lower if costs were the only consideration, but that may not give Sonos an equally good result where total profit is concerned, which is a fair way of assessing such policy decisions in any profit funded organisation.