Folks are probably tired of hearing my story. It seems these threads keep popping up.
I had two 4th Gen AE that weren't failing, but were not providing great coverage either. I was looking for something with movable antennas and was eyeing the ASUS RT-AC88U, but due to cost only, I opted for a Linksys EA8500 router and RE7000 extender.
Granted the EA8500 isn't as sleek as the Apple AE, but it sits in the basement, so it's no bother. I placed the RE7000 on the second floor wirelessly extending the network. Later, I changed this to hard wired and I'm able to get signal across our property.