Dunno that one but the incremental version of the Newker would almost certainly work with an existing stepper drive / motor setup. At some point there will be a step and dir signal to tap into. Even the old analogue controllers tended to have a step / dir output from the CNC controller before the signals passed through a "positioner" that generated the +/-10V control voltage. To my mind, there's a lot to be said for retaining the existing powertrain if it all works OK.

With the Newker controllers, make sure you don't get one of the "bus" versions, as they use some sort of serial bus to pass the positional signals etc to the (servo?) drives. The basic "incremental" ones send out the standard step and dir signals.

You'll notice that the screenshot of the controller in the link shows a 990TD (lathe) controller with X and Z keypads - but a 4 axis 990MD (milling) display showing X, Y, Z & A. The power of Photoshop!