CAC -its not a matter of upgrading the powertrain to take extra power. The airframe itself needs strengthening to take the extra power. The AH-64 is comparatively lightly built -its a fallacy to believe you can just keep increasing power without it having an effect .
As to performance -you obviously have no idea as to the effect of having ASPI on the U.S 'D' model .As it stands the U.K AH-64D will outperform a U.S
'E' model in terms of performance - the mod state and type of engine electronics doesn't come into it.