Best router?
Well, I bought a ASUS RT-AC66U a few weeks ago, and now I've sorted my modem out, it's FOOKIN rocks, the range is silly good. It's expensive but quality.
I have it in my garage and my mate 5 doors down can see it on his WIFI search, pmsl!
To OP: I'd check the simple things first...
1. Phone line... your master box into the house, all good? no loose connections, does main phone line work without crackling?
2. Modem/Router position... whack it straight onto your main incomer and test BB connection
3. Filters... get a new filter for your main line, these are notorouis for failing/drying out
4. All above good; do a ping test:
http://pingtest.net/ and compare
5. Employ a pro to sort you out in 30 mins :)