Three units (including the router itself) should have you covered assuming you can place them roughly center on each floor. Unfortunately, the satellites cannot be wired in at this time, but I do believe Netgear is looking at the situation. I am using the router and a single satellite in a ~4000sq ft home with a finished basement and it works great even with the satellite being connected wirelessly. Keep in mind the Orbi system uses a dedicated 5ghz channel as a backhaul so it does not work like a conventional router/extender combo.