  The Extremely Large Telescopes will require hundreds of actuators across the
pupil for high Strehl in the visible. We envision a triple-stage AO (TSAO)
system for GMT/GMagAO-X to achieve this. The first stage is a 4K DM controlled
by an IR pyramid wavefront sensor that provides the first order correction. The
second stage contains the high-order parallel DM of GMagAO-X that has 21000
actuators and contains an interferometric delay line for phasing of each mirror
segment. This stage uses a Zernike wavefront sensor for high-order modes and a
Holographic Dispersed Fringe Sensor for segment piston control. Finally, the
third stage uses a dedicated 3K dm for non-common path aberration control and
the coronagraphic wavefront control by using focal plane wavefront sensing and
control. The triple stage architecture has been chosen to create simpler
decoupled control loops. This work describes the performance of the proposed
triple-stage AO architecture for ExAO with GMagAO-X.
