If you end up running any wire, I would suggest cat out to a fibre media converter, make the long run to where your dac sits with optical fiber, then use another media converter for optical back to ethernet with a very short, shielded cat 6/7/8 cable.
Should not only “clean up” any analog interference from the router side, but also, as optical isn’t affected over that run from electromagnetic interference, you’d end up with a pretty dang clean signal to the dac.