If your current router connects and routes just fine and it's just the wifi you're looking to improve on then buy a ubiquiti ac lite, turn off the wifi on your router and plug this access point in to it to provide the wifi.
It's shape allows for better positioning which, combined with it being very good for its dedicated purpose, will give you better wifi performance than replacing the whole router. You also have the advantage of being able to use it if you change service to a different type of internet provider (VDSL to virgin for example)