I think that I have a pretty resolving system, Wilson Sabrina X's, Pass 250.8, ARC REF 6 and an MSB Discrete DAC with a Premier Power base and a full loom of Shunyata Alpha v1 cables. All my music is digital, either streamed or from my music server over the home network. To get from the music server in the next room, it had to go from the router down to the basement where all the house wiring (CAT 5e) and switches are for the network (at least 200 ft) and then back up again to the music room. I ran a straight Supra CAT 8 from the router about 40 ft. from the router to the MSB in the next room.
So, does ethernet cable matter? Well, a little. Yes, the system sounds slightly better, a little more definition in the soundstage, and the instruments sound slightly better. But I mean SLIGHTLY. Don't think that ethernet cables are going to blow you away, or be a night and day improvement. You will MAYBE hear a difference, and even that difference might be expectation bias, or an acclimatization to the slight sonic differences, making you think that they are "better" because you have listened to them for a while and gotten used to them, making you think that you hear slight sonic differences. Try switching back to the old ethernet cables and see if there is a difference and listen to them for a while too. In short, upgrading your ethernet cables may make a slight audible difference, but it ain't much for the money that I blew on running the CAT 8.