My personal option is to go directly to a true mesh system. Whenever people add more than a single wireless extender, it tends to cause more issue or they tend to have connections problems. True mesh systems like orbi are designed for more than a single access point (satellite) and they can dynamically change from star configurations to daisy chain configurations without issues. i used to use extenders and once I started going with a true mesh system, I haven't went back and won't.
and the option of keeping the Nighthawk AC1900 Smart WiFi Router(R7000) and adding the Netgear Nighthawk X6 EX7700 Mesh Wi-Fi compared to an Orbi System
If you're only using a single extender, its not a bad option. Again, if you'll only need a single extender, you should be fine. Once you move past a single extender then I'd be looking at a fully mesh setup. I've never had the fortune of using the ex7700 but it seems like a decent extender. I know its around $160 on amazon. If you look on amazon for a renewed (aka refurbished) rbk43 kit, it isn't a whole lot more.
