There is more to a Big Brake Kit then to just slapping on a Bigger Rotor and a 2 piston Caliper...
Lets talk about Britt's setup for example:
If you were to take the MSP verus Britt's BBK New setup
I've ran the car without ABS and on good sets of street tires that are fresh (Bridgestone RE-01R, Falken RT-615 and RA-1's). The car works great with the current pad setup that I have now which is a Axxis Ultimate Fronts and C-tek Semi Metallic Rears. Under threshold braking if I went any farther, the car would instantly lock up the front's at the intial bite and then continue to brake.
What am I getting at? I think our car (Mazdaspeed Protege) out of the factory is pretty well
balanced. A couple of pad changes can get the car to be better.
http://www.stoptech.com/tech_info/formulas%20_vehicle_braking_dynamics.pdf
Please visit this site for the formula
1. Torque created by the caliper on the rotor (at the wheel) = TW
TW = PS x AP x x 2 x RE
PS = Pressure of system; AP = Total Area of pistons in one half of caliper (one side of
opposed type or active (piston) side of sliding or floater type); = Friction Coefficient; x 2, since
there are two sides of the rotor that the pads are exerting force against;
RE = Effective Radius of clamping force.
This formula will give us a rough # of how much torque increase there is between the two brake setups...
We can assume the Pressure of System (Same Car) and Also the Pad Friction Coefficient (Same Pads Used) are the same.
Now we are left with
TW = AP x RE
AP = Total Area of pistons in one half of caliper (one side of
opposed type or active (piston) side of sliding or floater type)
RE = Effective Radius of clamping force.
Mazdaspeed Protege
Single Piston Front Caliper Size: ~57mm
Brake Pad Height (Acutal Contact to Rotor): ~56.5mm
Torque created by the caliper on the rotor (at the wheel): 3220.5
New BBK Setup
Dual Piston Front Caliper Size: ~40.5mm x 2 = 81
Brake Pad Height (Acutal Contact to Rotor): ~51.6mm
Torque created by the caliper on the rotor (at the wheel): 4179.60
That is roughly a ~22.9% increase of Torque created by the caliper on the rotor!
The Protege factory brake system is very well balanced for a stock system. I wouldn't want to change it for the worse just to save some money.
The amount of Stopping power might be increased in the front but that just means lock up will happen MUCH sooner. Trying to threshold brake will be impossible to acheive. Of course you can always change this with tire compounds and brake compounds but you are only putting bandaids on the braking issue and the car is suffering on other aspects of handling because of these changes. Don't get me wrong, there are ways to make this kit work but it's going to require more parts (Brake Bias, Master Cylinders and etc) and an extensive amount of testing to get it to match stock performance.