The Sonos HDMI cable supplied is already High Speed with Ethernet and can carry all supported audio formats.

And I suspect the amount of ‘speed’ necessary for an audio (ARC) connection is significantly lower than for a video connection. 

An Atmos music bluray will get up around 6MBps or so from what I’ve seen. An HDMI cable should handle even that no problems.

The supplied cable is appropriate for sending audio to the soundbar. Ultra high end cables are much stiffer and more likely to cause physical connector damage while you are struggling to install everything.

I think I saw a note somewhere that the TV to Arc cable only carried 720P video.

I’d worry a lot more about quality and not numbers. Stiff, off-spec ends, poor plating or internal soldering all far more important to avoid.

I have no idea what you just said

What he said is the cable supplied by Sonos wasn’t designed to carry high bandwidth video, but enough to handle the bandwith for eARC support, which is a different set of pins in the HDMI connection. 

Not sure I agree, I don’t recall seeing that note. But I do agree that the connection to the HDMI ports is important. 

Apparently eARC connections on both ends is vital for the best enhanced connection, whether it is delivering video or audio. But the quality level of the HDMI cable itself must also play a factor. That's why I asked the question.

Any HDMI cable of HDMI 1.4 (I’m pretty sure) has the bandwidth necessary to carry ARC or eARC on that part of the cable. Many manufacturers advertise bandwidth for video, but none that I’m aware of for audio. 

You could probably get a lot of data at Wikipedia on the various specs for HDMI. 

The video that is sent is the Sonos screensaver.

And I finally found the 720P note.

  From the above topic:

So HDMI 1.4 must be ARC, and HDMI 1.9 must be eARC. I need to remember that.

Remembering is a really good option compared to trying to find old topics here on the forums! :-)