@Temoshee 

That would work, the powerline would just be a glorified Ethernet cable.

The signal will still broadcast the same way so the range should be the same from the extender, but the speed may improve.

@Tony Thank you. Would it create a new WiFi network like the stand-alone repeaters do? I am asking because it seems like that causes interference on devices in range of both the router and the repeater. For years I have had a WiFi speaker that worked fine but when I added a TP-Link N300 with its own SSID nearby then it starting dropping the connection randomly. I am wondering if this other setup with the RE505X would be more of continuous broadcast, without interference, of the current WiFi signal from the router because the Amazon description calls it an access point. Thanks again.

@Temoshee 

The RE505X will create its own wireless network. I would recommend making the network name of the RE505X different from your main network. This will avoid a device potentially connecting back and forth between the extender and router since both network names are the same.

@Tony I gave the N300 a unique network name and it improved the connection on devices connected to the router's WiFi. I did not connect anything to the N300 network but somehow it makes the router's network more stable. Is that because the N300 is ultimately itself connected to the original router Wifi? Thank you very much for your assistance.

@Temoshee 

I think the N300 may have been switching networks so the connection would drop while it switched. Having unique names prevents a device connecting to another network when they should not be.