big brakes are a PITA, you have to run stupid big wheels and 15" gravels or winter tires are NOT an option withuot pricey rally-specific wheels that will clear. Cassidy's rally car runs STI 4-pots in front, and all the wheels must be fitted specifically, they are at least $200 each, and we need a sheetload of them.
I have run stock RS brakes/rotors with Carbotech Bobcat pads and Motul RBF600 fluid on the rally car for 3 seasons (gravel, snow, tarmac) and NEVER had brake fade, even when the front rotors are cherry-red from LFBing like an effin idiot. When I ran the WRX wagon (box stock brakes n fluid) as course opening for tarmac Rally NY, the brakes went away 99% and smoked so bad I thought the car was on fire. So you see that simple brake upgrades can make a huge difference.
stick with stock size stuff, upgrade the pads and brake fluid, your mod $$ is better spent on suspension/tires and driver training. Most ppl's "big brake" setups actually gain them little but bragging rights.