Not to jack the thread, but how 'bout we take alk/ca/mg out of the equation since we all agree that all three are vital to keeping a healthy SPS tank. So, since those three are handled, what would be the one thing your tank couldn't live without?
Personally, I would go with fish poop, but I don't exactly dose that lol. Sooooo, I suppose I would go with Kent's Coral Accel or Brightwell's MB7.