Morning, Im not 100% with the APEX controllers as I have never had one... but I believe you could set yo your own ATO using the controller (all that is needed is a lvl sensor (either optic of float) and a controllable plug with a pump in a RO reservoir. I have had the Tunez ATO and it worked great, but I currently just do what I explained before through the use of my Profilux Controller. As for dosing there are many stand alone units, but from what Ive read the profilux unit seems to keep everyone fairly happy. I will be picking one up in the not to distant future. Here is the GHL page with a list of their units:
http://ghl-direct.com/ghl-dosing.php
A quick google of "APEX DOSING" will give you some other options as well as some methods of programming.