Correct Jimmy Boy,
Front are generally direct bolt on, but I still believe you should upgrade to slightly bigger rotor.
Whereas rear is another story.
There are 2 approaches
Approach 1 - Special rotors + Adaptors
Special Rotor
A special rotor is required to fit this, DBA make one or you can source the Brembo rotor, which I have used.
Why special rotor?
The rotors require to have a
"OUTSIDE diameter (316mm) of the STi Brembo rotors, but the INSIDE diameter of the WRX parking brake. (Note that you CANNOT use the original WRX STi rotor, because then your smaller-diameter WRX parking brake will not reach the rotor.)" Copied from
http://www.fastwrx.com/rebradkit.html
The WRX parking brake is 170mm, whereas the STi one is 190mm.
The special rotor accomodates for this.
Adaptors
People usually get their brackets made up, but a lot of them look pretty dodgy. So I've been looking around for while and finally found a place to get genuine Brembo Brackets.
Approach 2 - Shoe Horns + Adaptors
Shoe Horns
PHATGT has used this approach, this allows the rear brembo to work with our parking brakes. Good thing about this is that you don't have to use a DBA4000 rotor. You can use other rotors e.g. Dixcel or 2 piece DBA 5000.
This is all I know about it, I didn't really research much into this. Tangcla can fill in more maybe.
Heres pic of the shoe horns.
Adaptors
Same as used in approach 1.