I went from using an SPDIF cable to a cheap, short HDMI cable into my Musician Pegasus DAC and the performance upgrade was significant although this is specific to each DAC given the unique design of its inputs. I’ve heard others say that upgrading to i2S is much more significant than the quality of the HDMI cable and that the HDMI cable should be as short as possible as it wasn’t designed to travel distance. I chose the 6” version of this cheap Monoprice cable because it was the shortest I could find and experienced a huge upgrade over SPDIF, and although I’ll eventually upgrade to something like DH Labs I’m certainly in no rush given the sound quality I’ve got now for only $6.50. Do your research on what input is best for your specific DAC, and if i2S is recommended start with this cable and see what you think as there’s very little risk.
https://www.monoprice.com/product?p_id=13578
Hope this helps, and best of luck.