The RKL is limited to 4 modules. The NET and HUB modules do not count toward that module count. The RKE has a limit if I remember correctly it is 63 modules. I don't know of anyone that has reached the real limit on the RKE. I am not sure on the Archon but it would be at least the RKE if not more. There is also a 8 outlet module now the PB8.Profilux>Apex>ReefKeeper>ReefAngel>others
While the Profilux is awesome, its lacking support which is a main thing when it comes to conrollers. I had a RKE and switched to Apex which I'm very happy with so I just bought a second one for the office Tank
RK is limited to the number of modules and unless you upgrade to archon, you will eventually want internet capability and more than 4 plugs... most likely you will need two outlets for dossers (Ca and Alk) and 1 or 2 for lights and circulation pumps... Cant control the heater, fan and so on in my opinion, so I say go with a Apex.
Also since the most popular controller is Apex, it will retain its value in-case you will look into selling.
