In general wi-fi is meant for single room. Even there's relative thin brick wall in between, it will influence fast 5GHz band -especially if signal needs to travel somewhat diagonally trough the wall.
Also keep in mind, that PC case itself is a disturbance in 5GHz signal path. Means, if your back side of PC case is oriented away from wi-fi router, then antenna(s) connected directly to PCIe card won't perform good -you should prefer standalone antenna which is connected to PCIe via cable. Ok, $50 isn't that big money, so it's maybe worth a try.
I never tried powerline adapters, but from what I've heard from friends, it might be better solution for room-to-room connection -I would probably choose that solution.
Anyway, cable is to be first choice: is very cheap, simple and very reliable.