dont forget that you want to make sure that you want good brake bias. If you do the fronts, you really really really should do the rear as well. If you dont, you'll have way too much braking at front and non in the rear.
Also, remember that with bigger pistons or more more pistons, you might have to increase the size of your master cylinder, or run two master cylinders. The increased need for pressure with bigger pistons and/or more pistons usually requires a more powerful master cylinder (bigger bore).
If you want the best in brakes, check out movit brake systems. They modify Porsche 911 brakes (usually the twin turbo's) to fit many makes of cars. They also include the correct machined caliper brackets. Their website is
www.movit.de