Its common to all Subarus unfortunately. 1 out of 8 front brake jobs result in a broke or damaged caliper bracket bolt, the 17mm. Not so much on STIs. that's why we have a few bolts in stock. Just like Boon said. If you break the bolt then you can hammer the caliper bracket off, the bolt can be persuaded thru the knuckle hole, put the bracket in a vise, add heat, muckle onto it with vise grips and twist.
Boon, Glad you got it done. What did you get for brakes? I have to do mine soon. I'd like to do an upgrade but I guess it depends on my paycheck. Mine could end up being Car Quest, stock Subaru, maybe Hawk and Power Slots. Also, I'm hearing WRXs and NA Imprezas upgrading to the 05GT with good results.