Am pleased they seem to be doing the job. At the end of the day you can't beat a wired connection. Direct Ethernet is best, followed by powerlines and wifi is most unreliable. I've had it where wifi goes awry in certain zones for no reason. And no amount of channel changing will cure it. Some devices cope better than others. All it takes is for someone next door to maybe install a baby monitor or video sender behind a nearby wall and it can swamp the 2.4 ghz spectrum around its transmitting area. Bluetooth being on or used nearby can also halve throughput. 5 ghz wifi is better assuming your wifi dongle/card and router supports it, but only because less things use the 5 ghz spectrum. Once more people and devices catch on this spectrum will get crowded out to. Although 5 ghz has a weaker output distance so walls are more likely to stop it in its tracks. Means 5 ghz signals less likely to infiltrate your area other than your own. At the end of the day it's a balancing act and it sounds like your powerline solution is the workaround. If you want to get really technical you could even use a spare router Ethernet plugged in to the Powerline upstairs and set it up as an additional wifi access point on a non overlapping channel to your router. Then you have strong wifi upstairs as well as down. Your machine may cope better with the much stronger signal and overcome the interference. It's worth checking your machine doesn't make a Bluetooth connection with anything. I don't use it myself but I know on my iPhone that if Bluetooth is active then I lose half my 2.4 ghz wifi speed on it. To get round it I use its 5 ghz capabilities instead.

cheers, Wayne