And this is to the point on which I think Stoptech meant to speak:

We don't NEED more pistons because we don't need a larger pad surface on the rotor. If we were endurance racing and were severely worried about pad life then we'd all have 6, 8 or 12 piston calipers. We also don't need more brake torque than what is provided in a four piston or extremely small six piston caliper. I believe that anything above and beyond this is detrimental to pedal feel.

For our Audi S4's that do street and track duty and retain the factory master cylinder, we don't need and can't really begin to utilize any more than the smaller of the available street kits.