My parents have a ranch style home with an RT-N66U at one end, and a TP Link TL-WA855RE (300mbs) extender in the middle. I'm trying to figure out the best way to improve performance. I have an extra Asus RT-AC68U. Should I buy another AC86 and connect as mesh? I also have a Google Wi-Fi 3-piece router set that I bought at a yard sale. The problem is, neither the AC68 nor the Google set are tri-band. The Google WIFI Pro with tri-band is too expensive and gets too many bad reviews. How much difference will tri-band be with it's own backhaul? Should I just buy a couple RT-AC3200 or RT-AX92U tri-band routers, or will dual-band be good enough? This won't be for gaming.