Lots of good product for a Legacy or any other large vehicle (have 1521s on my E450 RV). Street and lapping pads mean a compromise - because they won't give the stopping power during track duty and they'll dust more/make more noise than some want for street.
That being said, Carbotech's AX6 is designed for AutoCross. It's a great pad and I use it on my daily driver RX8 year round. If you're only going to the track a little bit. If the time attack was very light. They'd work. Give me a call and we can chat more about what you're looking for and how Carbotech can help. I'm sending you an email, Joe.
A great way to handle track and street is that you can use different Carbotech compounds WITH the same rotors - so you'd only swap pads rather than the typical swap of pads and rotors.
Note: this is only with Carbotech compounds. If you are using Carbotech and another brand of pad then you must swap rotors.