A:
Don't buy an extender but buy a better router. I had this issue and went through the time of buying one after another and returning them not liking the results only to find out i was extending a mediocre signal. The best bang for your buck is to sell your existing router, go eat a nice lunch, and pony up for a $200 router. You'll get like 5000sqft!
*NETGEAR - Nighthawk Dual-Band Wireless-AC Router
*Asus - WirelessAC1900 Dual-Band Gigabit Wireless Router
*Linksys - SMART Wi-Fi Dual-Band Wireless-AC Router
*Asus - 802.11ac Dual-Band Gigabit Wireless Router