Then Just put the router near the centre of the home and at a higher position a single router should do the job. The most add an extra router 710 but unlikely. My 4 room whole house 1 Nokia ONR already can cover. Unless your router location no good and the router is at low position.
Ok, i think should be consider high (head level) and near middle.
but then do you know if EB810V and HB710 signal coverage range? Wondering if should change to HB710 instead and save some money.