I would say a router upgrade would do wonders. I recently installed a mesh wifi system at my house, and now have excellent coverage throughout. With just one router, there were always spots where performance suffered.
I would recommend checking out any of these solutions that you think would fit your needs:
https://www.pcmag.com/roundup/350795...etwork-systems
I bought the
TP Link Deco 3 pack when they were on sale at Best Buy, and have basically eliminated any frustration I had with my home wifi.