You can buy an aerial for the NDS separately, not expensive. Try WiFi and see if you get a decent connection. If you do, it might well sound better than the over-the-mains extension.
With a little imagination you might find a way of running an ethernet cable between the two floors until you move onto the same floor.
Otherwise I would wait until you make that move before fiddling with switches and posh cables.
WiFi performance is not the strongest feature of the NDS. If you really can’t manage an Ethernet cable I would consider a decent Mesh WiFi setup. Put one of the satellites near the streamer and connect it with a cable and you’ll bypass this issue.