Help with choosing the right router

Hello, 

I need some help and advice. I am not a tech person at all and need to purchase a new wifi router for my home. I have about a 3500 sq ft home and have several devices on the internet all the time. My current wifi network is poor as I live in the country and only can get a certain speed. I am planning to switch to a tower internet service to see if this can help with my internet speed. Right now I have 2 different internet lines coming into my home and 2 different routers just so I can get a decent speed. I work for home fulltime and need reliable internet. I am on the market to buy a new Router as I am switching service provides. My question is what router do I purchase with this size home. I need coverage in my home in the basment up to the 2nd level. Right now the internet connection is very spoty. Can someone please recommend the best router for fast and reliable coverage as well as for this size home. 

Thank you very much

Jenny