URL regarding the Alcon Super Kit http://www.alconusa.com/client_images/files/92_1177.pdf
I have had both Alcon Super Kit and Brembo GT. The Alcon kit is more aggressive in terms of breaking power. Brake pads matter a lot. I haven't tried the Brembo GTR yet, but the Alcon truly response more aggressive than Brembo GT even with the same pads.
I will pick Carbotech for brake pads because of the price and availability.
Also the size of the rear discs on our cars don't really matter as i believe 70% of the braking power depends on the fronts.
Hope the info is helpful for you.