well your first starter poin if it aint 4 pot subaru calipers, is get subaru 4 pots and discs with a good set of fast road pads. Braided brake lines and good brake fluid.
you'd get 4 pots and stuff for about 250, a lad selling his in for sale section Rhuadhri555 (For 250), 50-60euro for braided hoses, same again for good brake fluid, and good pads 60-100 euro.
Then the option of brembo's, more expensive.