Most routers have roughly the same wireless range so changing the router may prove to be a waste of money if all you are seeking is better WiFi. I recommend you keep existing router and instead buy a wireless extender and place it midway between router and room where wireless range is poor.
That's what I did, problem solved. I bought this one to extend range of my Billion router:
http://www.amazon.co.uk/367/dp/B00XYEPLXU/ref=sr_1_12?ie=UTF8&qid=1441263262&sr=8-12&keywords=netgear+wireless+extender