Two types of stepper motor drivers are utilized on the Rumba control board - the DRV8825 is configured for 1/32 microstepping for the XYZ steppers. The Trinamic TMC2100 which features 1/256 microstep interpolation is used for the extruders which provides extrusion consistency and speed.

Here it is with better heat sinks and a few other tweaks (more or less the current configuration):

And buttoned up to contain the madness: