If I remember correctly, I believe the gas generator of the PT-6A-66 has a thermodynamic output capability in ISA conditions of around 1650ESHP. Of course, the gearbox is only rated to 950 SHP and presumably the bang from the gearbox would precede the flames from the gas generator as the turbine blades burned up!
It might indeed be described as an 'afterburner' by that point!