My comcast router dual band wifi is mainly for my (Xfinity) 2 Smart Tv's but also for my wireless laptop , tablet and (verizon) cell phone. Router is down stairs with one tv. The other tv is upstairs and laptop and phone used various spots in house. WiFi is terrible throughout the house Except for tv's. Is a wifi extender my solution and if so what do you recommend? Or do I have some other problem?