re: Better to buy WiFi extender or a whole new router?

Excellent advice however not everyone wants to or is capable of going through the trouble of wifi signal propagation troubleshooting. I am in IT and am perfectly capable of setting up any network solution that I want but made the decision that I just wanted a "no fuss" wifi at home. I think that the average tech board poster asking for wifi advice probably needs the same thing.

Once we start getting into measuring wifi strength, running Ethernet drops or configuring AP's many people are thinking "screw that".

This is where the majority of the current mesh systems hit a homerun. Easy or no configuration needed, if your results aren't perfect out-of-the-box just move a node to another outlet. If your wifi needs change add another node(s) later.