Here's some helpful info I've put together elsewhere
Thread about swapping subaru brakes:
http://forums.nasioc.com/forums/showthr ... p=18085854
Might be missing a little bit of info specific to newer legacies so I'll have to update it.
Here's all the different brakes on pretty much every subaru in north america:
http://forums.nasioc.com/forums/showthr ... ?t=1529797
and a general brake FAQ:
http://bbs.legacycentral.org/viewtopic.php?f=8&t=30989