So for starters, I have never been into cables, that was until I found my main IEM, the U12t. I started just wanting to have the versatility of having the option to go balanced and single-ended whenever I wanted, thus I gave the Kinera Leyding and Qoa Rum a try. Both the Kinera and the rum are under $100 so it is not really fair to compare them to the Eros S but it is what I have as experience.
The u12t sounded way more narrow with the rum and Leyding cables, I loved how they looked and felt but being someone who is into classical, jazz, orchestra and those sorts of genres, I could not sacrifice any of my soundstages. Eventually, I decided to just go Big(big for me being 300 usd) and I went for the Eros S, the cable from effect audio has a superior built to any other I have tried, including the premium cable that started coming with the u12t during the last year. I honestly did not hear a dramatic difference but what I can tell you is that with the stock cable, I was only satisfied using the MX module which lowers the bass and gives you a wider soundstage, however, now that I am using the Eros S, I feel I have an equal if not wider soundstage while the m20 module which isolates the iem and increases the feel of the bass.
I won't tell you to buy it, but if you already have the IEM you love and you want to enhance it a bit more (especially in the aesthetics department), then go ahead.

ps Last I checked the only place that had the Eros in Stock was audio46.