For 15", the pickings are definitely slim. I opted for Toyo T1Rs, and I'm pretty happy with them so far. I drive my car mostly on the street, but have about 6 or 7 autocrosses on the tires, plus one lapping day (over the course of the last 2 summers). The tires don't have the stiffest sidewalls, so I'm finding that autocross is pretty hard on the shoulder treads. I'll likely replace them next spring/summer, which is about what I expected. Tread-wear rating is 280 on these tires.
I thought about trying to stick with the original sizes, but was unhappy with the selection of matching 195/65; 215/60 rubber. The sizes I went with on the T1Rs were 205/55 and 225/50. The shorter tire makes for shorter gearing, which is slightly annoying on a long highway trip where I'm turning 3400 rpm doing 120 km/h, but for autocross, it is helpful. The 55/50 stagger makes for matching front and rear rolling circumference and looks decent in my opinion. Some say that 205/50 on the front looks just too short. Lastly, the smaller size introduces a speedo error - I'm about 10 km/h slower than indicated.
This is a good shot of the tires, but the suspension is fully loaded up front, so it might not give you a good idea of how the front tire fills out the wheel well.
This picture is pretty grainy, but shows both front and rear profiles well, as the car sits.
