I don't find it hard to believe that you'd find a difference when the cable is used from the SL outputs carrying SPDIF over AES/EBU. Carrying network packets between the core and endpoint, though, I'd guess the previous cable may have been defective, or lacking in basic spec in some way?
E.g., I was getting constant dropouts using what I believed to be an OK Cat 5e cable when I first got Sooloos, and switched to some individually made/fluke tested cat 6a (using Cat 7 cable - once you put Cat 6 termination on them, you can't really call them Cat 7, can you?). I haven't had any dropouts since, but didn't particularly notice a sound quality upgrade even then.
To put my comments in perspective, I've owned very expensive cables in the past for analogue interconnects, speaker cable, and still run specialist power cables where I feel I could/can hear the difference, I just haven't noticed any difference in network transmission above and beyond a well specified and properly constructed cable, although if you can, that's the thing that matters!
Note, however, to qualify the above, that general standards of spec/manufacture are possibly poor. If you can, the best way is to buy a cable which has been individually tested. Blue Jeans cable offer this in the US, and so do
Universal Networks where I bought mine in the UK. I can vouch for the quality of the latter, I now use them as patch cables for networking, not just hi-fi, and they come in lovely colours too
