Do modems / routers matter (beyond speed)

My cousin has a brand new Cambridge Audio streamer, which he's using wirelessly. He asked me if a wired connection would yield improvement in sound, and I had never considered as I don't have the option to do so in my house. He told me his router is about 5 years old, but is getting 50 mbps download speed. He has a Cambridge Integrated (CXA 80) and paradigm prestige 85 speakers.   His modem/ router is in a different part off his house so he cannot simply test this, so curious what others have seen, and whether with his equipment it would be noticeable.