Need a help! Can anyone tell me what are the relevant differences that may be decisive for purchase ? I'm between the choices (ARCHER VR600 v2.1) (ARCHER VR900 V.2 or 3) (ARCHER AC2800) Please, Notice the fellowing : I have house of 3 levels (Each level has about 200 M²), Meanwhile we are 7 users. THANKS IN ADVANCE.