Soft water is [subjectively] good for a stout anyway, as long as you aren't going for a super dry, Guinness style. RIS, big and smooth - soft all the way.
So, no, I wouldn't worry about water salts. You need to have a good idea about what your mineral content is to begin with to do good adds, anyway.
Primary: BM's OktoberFAST
Secondary: What sorcery is this?
Kegged: Thunderstruck Pumpkin Ale, It's The End Of The World... Stout, Cider
Future: Alchemist Heady Topper Clone, Yooper's DFH 60 Minute Clone, Session Bitter