The powerline solution worked for me. It also cured my intermitent disconnects over wifi.
The wifi issue may not be a problem with your own hard line internet / indoor network. It could be your neighbour or somebody very nearby with a high strength system knocking yours. Wifi is now becoming so omnipresent that the rf spectrum used for it is becoming congested. Currently most wifi is on the 2.5ghz band, if you can, move to the 5ghz band. It does not quite have the same range but there are less systems currently using it.
Longer term the powerline system works well, but will eventually suffer the same issues of contention.