Here's my plan:
Swaybars are fairly straight forward to install, especially the rear one. They reduce body roll and dial out a bit of understeer. This I will do.
A car with this much power deserves better tires. At a minimum, buy a good set of high performance all seasons like Dunlop SP5000 or the like. A Plus One upgrade to 17" rims is even better. This I will also do.
Get a performance alignment. add some negative camber in back, futz around with the toe in (to the extent you are able; Subaru doesn't give you much to work with). My last Subaru was transformed by this, as it quickened turn in and made the car feel more "dialed in." This I will do very soon.
Springs- I am not convinced that the improvements just springs bring to the table are worth the hassle of installing them. Certainly not in my top 3 list in terms of importance. Heck, I'll probably do XM radio before I turn my attention to springs. I do think the car looks better dropped a little, and Peaty's car is a great example, but I'm pretty happy with the damping rates already. Having sais that, I may change my mind after an autocross or 2, but so far my explorations of the car's damping rates have proven quite satisfactory. I think swaybars and tires are going to make a more dramatic diference, and springs would be the icing on the cake that makes it a complete visual and performance package.