Can you connect a computer in place of your streamer and run some tests? Link speed, ping . . .
Ethernet cables improving audio is a debated topic. IMO, you are already wired, which is much better then wireless and 70 feet is not very far for Ethernet at the audio streaming speeds. Other will disagree. If the testing shows a good link speed, I would look at other aspects of your system to upgrade but without knowing more can't comment.