Increasing the amperage will not nake the bell louder! The actual current through the ringer coil(s) is determined by the voltage and the resistance/impedance of the coil, so unless the current transformer is grossly undersized a larger transformer won't help.
Incresing the voltage will do though. Only works with classic bells of course, not with electronic chimes.
Outdoor bells for factories spring to my mind, they're incredibly loud so they can be heard over the noise of a factory yard or school yard during recess.
