Unless your car isn’t running correctly, or you see oil dripping on the ground where you park, I’d say this useage rate is within the range of normal for using that light-weight of oil. I expect the usage might be more in summer b/c of the warmer temperatures. Esp b/c the summer has been pretty hot in many areas. In the winter you might find you get more miles per quart.
I had a VW Rabbit back in the early 80’s that used a quart in 500-1000 miles, and that was considered “almost” normal, and it was 10-40W oil. For another reference, my early 90’s Toyota Corolla uses about a quart in 7500 miles, 10-30W oil.
Suggest to monitor your oil level, and when it is a half-quart low top it off, unless it is time for an oil change anyways. Not satisfied? You could experiment with a heavier weight oil and see how it affects the usage and mpg provided that is acceptable to what the owners manual says.You might also Google “Subaru Imprenza oil usage” and see if you find anything interesting. There may be other forum discussion on this topic.