You haven't indicated what you'll be brewing.
No matter really though, as the only batch I've modified water for here was a british bitter, added a bit of gypsum. Everything else has been right out of the tap on the northside.
For your first batch on all grain, I wouldn't worry about spokane city water. Dozens of 10 gallon batches in, and I've yet to get my system to a point where I'm worried much about modifying water - I've other areas of my brewery with more pressing needs. If you're brewing this month, I'd be more worried about subzero temperature as a high for multiple days. Makes temp control a bit tough both for brewing and fermentation. You'll get much more off-flavor from off-temps than you will from water here.
Hope that helps