on second thoughts. this might help you decide on what to do about your brakes..If you read it, you won't just want to update your calipers any more.
What you want is more potential to absorb and get rid of heat cause brakes turn friction into heat, and when the overheat they stop working cause they cant turn any more friction into heat.. erk.. crash.
Big discs dissapate more heat which is what is generated when you apply the brakes. This is because they have more metal to heat up, and more surface area to radiate the heat out through.
Having four/six/ten smaller pots in a line moves the clamping point further out on the disc, so it has more leverage and a more braking power for the same force applied through your tootsie.
So bigger discs mean you can brake for longer, and multi piston calipers mean you can brake harder .. till you lock up.
if you can, get an alloy caliper, they are lighter than the cast iron ones you find in some kits. Plus they usually have little heat vanes, like a heatsink on a pc cpu, to help dissapate even more heat
hope this helps.
JB