I think Balling is a much easier and less risky alternative for your tank size where running a full scale CR may not be practical. A lot of European reef tanks run successfully by Balling method, but once the volume exceeds a couple of hundred litres, Balling can be expensive. Note: The Grotech liquid additives come in 5L pack too
2 channels enough, you do not need KH+Ca3 as it is formulated for those using RO water.