I think the area where you live, water is hard so its not very hard to go with the decision of not changing the natural water chemistry. In my case though, it is on the borderline. But I think I will go ahead without any additives and will monitor water condition often and see what happens from there...
This sounds like the best bet to me. Once you get into chemical buffers it becomes difficult to maintain. It's better to have a steady pH and hardness than to have it fluctuate.