HDMI audiophile cable

Save your money - unless you've got a neurotic itch to spend more because of confirmation bias. Any well-made HDMI cable will transfer all those data bits just all well with no loss just as good as an expensive cable.

You mean, just like any digital cable?  Because I’ve heard huge differences between digital cables running between my DAC and preamp.  If you don’t hear differences,  good for you, but I’d get my hearing checked i I was you. 

If you feel the need to spend money go ahead.  But your DAC already has a circuit to convert from USB to I2S which is exactly what the Singxer does.  In other words, it duplicates exactly what you already have.  Unless you have reason to believe it will do that much better, and noticeably so, there's really no need.

Devices that can transmit the I2S AND eliminate the USB function entirely might be expected, theoretically, to improve SQ.  Typically they have Ethernet input and I2S output.  But that's not what a Singxer SU-2 does.

@soix I think you have this figured out yourself already, but getting advice on anything audio from Jason Bourne is like getting advice on the virtues of Christianity from a Taliban 😂😂

For a i2s HDMI cable I would recommend one of the discontinued previous generation HDMI cables from Audioquest. Music Direct has them occasionally at deep discount. I got a pair of Vodka for my Esoteric SACD transport a few months back at less than half of. Previous generation non-48 which still good for Audio purposes.

I used to own the Singxer Su-1 several years ago. I recall the best thing I did with it was modify it to use a linear power supply, Kitsune in California had a mod kit back then for that purpose. It was transformative in SQ. Serious. Having said this, I am completely unfamiliar with current generation of Singxer. This is just from my previous own experience.