AMG boss Tobias Moers told Autocar that the A-Class-based coupe and small SUV would not have to wait for their respective facelifts for the upgrade.
Both cars will also get the same technical upgrades as the A-Class at the same time.
The revised A45 gets a 21bhp boost of power for 2015, taking its total output up to 376bhp from 355bhp. It also gets an increase in torque of 18lb ft, so it now has 350lb ft at 2250rpm.
This boost in power has translated to a 0.4sec improvement in 0-62mph acceleration, so the dash now takes just 4.2sec. A similar improvement on the CLA45 AMG would translate to a 0-62mph time of 4.2sec, while the GLA45 AMG would take 4.4sec.
The other technical changes on the A45 that would be carried over include a revised seven-speed dual-clutch automatic gearbox with shorter ratios for quicker response times, and a new mechanical locking front differential to improve handling. The fuel economy and CO2 emissions figures remain unchanged on the A45 and are expected to do the same on the extreme versions of the CLA and GLA.