well i'm not a physicst, but dont the big rotors offer better braking? i mean bigger diameter thus calipers dont need as much force/grip on the big rotors as compared to the small ones, when braking..
changing to 2 pistons or even 4 pistons..without changing the tyres for more grip? dont you think that it might gonna be a little bit scary when panic braking?
if u rich enuf, try aprilia's mx125 disc + calipers.. those disc r gorgeous.. i inquired bout the price here in singapore it cost sgd700 = usd350++ dunno whether they trying to con me of my money...