I don't think you'll have any problem but it's hard to be sure.

In general running the wires in parallel is bad. However your speaker wire is carrying relatively high currents while the ethernet is low current. Also the ethernet wire is twisted pair which helps limit radiated emissions.

Best to test it. Can you run the ethernet next to 9-feet of exposed speaker wire to see if there cross talk issues?

If you can keep the ethernet on the opposite side of the channel created by your wall studs that should be enough separation to prevent the cross talk.