New router confirms AC 5Ghz improvement, but range extension needed?

Ok so I chucked in the HG659, indeed the speed a remarkably better in close proximity.

I put an AC receiver USB chip on the notebook, it helped a bit.

But I need to extend the range.

Outside the room is the long corridor which is in line of sight of the router. It has a power point. If I placed an access point or range extender there, it is in line of sight of the bedroom. Would this be the best course of action? If so what type of range extender should I consider?

I read this article

http://au.pcmag.com/d-link-wi-fi-dual-band-range-extender-dap-1650/47829/guide/the-best-wireless-range-extenders-of-2018