-1.5 is fine. Actually, you probably won't quite be able to get that much, but whatever you can get will help. It won't cause awful street wear IF you make sure your toe is within 1/16" or so, in or out. I personally ran a really crazy alignment the last 2 years or so- 3/8" toe out front, -1.6 degrees camber, 3/16" toe out rear, -2.5 degrees camber (until I got the Volks; then I had to go to like -.6 degrees rear.
However, my car has awesome autocross handling, no crazy tre wear, and was really fun to drive.