Congrats.
One note: the Sage One is significantly more powerful than its line rating. This was also true for XP and Z-Axis in the lower line weights.
For example the 5wt Sage One has an Effective Rod Number of 6.5, meaning that you may find it tosses a higher line weight much better than the 4wt. (like 5wt or 5.5wt)
Regardless it should be a great setup for stillwaters.
I agree, the one is a VERY fast rod and can handle a one line overline, but you also need to remember, most lines out there (RIO, SA, CORTLAND) are 1/2 line weight overweight from industry standard as they are.
Depending on what you plan on doing with it, I would look at the RIO indicator in a 5wt if you are planning on Chironimid fishing, etc.... but if you plan on doing alot of dry fly with it, get the RIO gold in a 4wt (More delicate presentation that a 5 wt would give you)
Rick