Don't forget about RA (residual alkalinity) as it will play a part as well. I use phosphoric acid to drop mine for lighter styles like pilsners. But then again I dilute my water with 30% distilled water, then use gypsum and calcium chloride to acheive the appropriate sulfate to chloride ratio for what I am brewing.
Water matters! If anyone tells you it doesn't matter already has great water or they only brew one kind of beer!