I have the Asus AC66U and it works fantastic across three floors. My house isn’t nearly as long (around 40 yards) but one router across three floors of mostly wood has been pretty good. I’ve been able to play Bf3 consistently without lag while my brother, girlfriend, mother and her boyfriend are all on Netflix or browsing.
I initially planned on adding some wireless repeaters but I haven’t noticed any signalling issues in the past couple of months yet.