I purchased the TP-Link MR600 v2 4G+ router and it's working well so far, but the wi-fi connection doesn't sufficiently reach my office which is a floor above where the router sits in the lounge. I live in a building made of brick and concrete, so I presume that is why the connection doesn't reach between floors. There are so many TP-Link Wi-fi extenders, can someone recommend which one I should get?