4 pot callipers? go home suck donkey balls.
THis is DA MAN. 15.2" brake disc, 12piston calliper
http://www.lltek.com/PRS_bin/PRS_84_12_piston_brakes.htm
And I'm not gonna ask struat_little to use google, because somebody might flame me.
Typically, the more pistons/pots you have, you will end up with a fairly big brake disc, and that help with the leverage in the first place, that is your source of better stopping power. And of course, better cooling.
More pistons also helps with a more even pad contact and improved better brake feel/modulation. (not sure how true this is)
The jump from 1pot to 2pot enables a system to use floating rotors, and the upgrade to 4pots helped even out the pad wear alot. Then, some companies started with 6piston callipers to fit bigger pads with a bigger contact patch, and then it gained fame. Hence the legend of "the more pots the merrier". IMHO, kits like the above shown are crap, and used only for rice shows, or the bling factor. Your tyres can only do so much braking, and there are no two ways about it.
Somehow, alot of people spend money to upgrade to 4million pot brakes, but still use sime astar tyres....they must be damm confident of their stopping power then.