I used 08-14 WRX caliper brackets; however, any 02-05 or 08-14 WRX bracket will work. I think the Crosstrek bracket works too as that's where I got the idea from. Rotors can be from 02-14 WRX or other Subaru. It is a very common size for Subaru (294mm). Your 4-pots will bolt up to the Impreza with the 294mm front rotor but you will have to consider wheel clearance.
Here is a thread on rotor sizes.
https://forums.nasioc.com/forums/sho....php?t=1265631