best Netgear extender for AirPort Extreme

I have the latest (last) Apple Airport extreme router that works well in a 4,000 sq foot home on the second floor, but doesn't have a strong connection at the main floor family room and backyard. I was considering one of the Netgrea Mesh sytems but perhaps a single unit extender would do the job more cost effectively.  Any suggestions would be appreciated.  Thanks. Rob