First off:
Welcome to Reef 2 Reef!!
These are the kits that I use:
Cal = API or Salifert
Alk = Hanna Alk Checker (API will get the job done too)
Mag = Salifert
Nitrates = Salifert
Phosphates = Hanna ULR Checker, but maybe switching to Elos in the future
This is exactly what I use..no problems