Required. You stock tires are worthless in the snow ( since they are summer performance) I opted for a set of 16" alloys and Pirelli snow tires from tire rack. I went with a cool wheel look because it will be on the car for nearly 1/2 the year here and I didn't want steel. The price difference was minimal. I went with tire rack recommended snow package size for a 16" wheel for my 11 wrx.
Good luck, act fast!