I2S Recommendation

1) If the equipment manufacturer recommends an I2S cable, then you should probably follow their advice. PS Audio is another brand that recommends using an I2S cable for their DAC's. There is a lot of positive comments regarding this subject on the PS Audio forum. 

2) Check with both the DAC and Cable manufacturer to be sure that the cable you are interested in has a compatible "pin configuration" before buying the cable in order to avoid buyer's remorse.

3) +1 on the DH Lab I2S able. I find them to be a company that usually offers a "good bang for the buck" product.

4) When in doubt, don't start with an "entry level" product; but, don't start with a "top of the line" product either. Find a middle ground product that suits your budget and then go from there.

Best of luck and happy hunting!

I don't know there is a sound quality penalty paid for using HDMI cable vs I2S, but you're paying for unused runs of wire, in the case of pure silver this can really run up the bill.

@audiostick I was similarly unable to find any info on the Voodoo Silverstream. Tried it on a blind buy since it was not very expensive, and was surprised at the sound quality being pretty great.

In my current headphone system (using Denafrips Gaia DDC, Denafrips Terminator 2 DAC, Holo Audio Bliss KTE headphone amp, and ZMF Caldera headphones, with some components being in flux as I figure out what I like) the Voodoo had the best detail of any other model I tried. Not overdone but could be a little bright at times, so you'd want to watch the system matching closely. With the right gear though it was pretty magical. 

The DH Labs was slightly behind in detail and resolution but made up ground by having a more fleshed out midrange/low end, which made for a better balance overall. I would not call the Voodoo "thin" in isolation though, just after direct comparison. It's possible or likely that in some situations the Voodoo is a better choice. 

@mitchagain Regarding your point number 2. My recent I2S HDMI adventures have shown me that almost all of them use the same HDMI standard (which is official, sort of like USB), and it is up to the DAC and transport or DDC designers to determine what pin configuration they use. But the cables themselves are almost universally standardized.

I did come across some custom builders who would special-make an HDMI I2S cable to enable going from say a Pink Faun streamer to a Denafrips DAC (they use slightly different pin configurations from one another) but this was pretty rare. That means mostly you can just shop for any HDMI cable and you only have to worry about the standards used by your DAC and transport. It also really helps that some brands let you choose multiple configurations either via hardware switch or in software. 

I will add Revelation Audio Labs HDMI I2s cable to the list of suggestions. I have one that replaced my Tubulus Argentus, the solid core silver is much smoother midrange with all the details, better soundstage width and depth. 

I tried the DH Labs and RAL i2s cables.  At first I thought the RAL sounded better, but went back months later and did some extended listening switching back and forth between the two, which is easy and can be done quickly since my server and DAC both have 2 i2s connections.  I couldn't tell any difference between the two.  I chalked up my initial impressions to confirmation bias.  I'd get the DH Labs cable.