Orbi in Garage

I currently have the Nighthawk 9000..   thought it was suppose to be the best... now they tell me Orbi is what I need.  I purchased 2 Night hawk Mesh extenders ...   my router is at one end of my house, I put the first mesh at the other end, and the second in the garage... the one in the garage works sometimes and most of the time not...  So Neatgear said I need Orbi...  I'm looking at the Orbi RBK50 ... I think it should work from what I've been reading... my question is ... do I purchase 2 Sat.. or 1 Sat and the Orbi Outdoor for the garage... 

thanks