I'm looking at your picture and trying to figure out what's going on. It looks like you've got two frames mounted vertically, quite close together, that each have a narrow stage which moves up and down. Is that correct, or should the picture be turned sideways? Are you planning to span those two stages with another axis? Do you have a drawing of the whole machine you're envisioning? That would really be helpful if anyone's going to offer meaningful advice.
In general, though, you should decide if you're making a machine for wood or steel. While similar in their functionality, these machines are actually quite different, with the former being much easier to pull off. That spindle, for instance, is okay for wood, but much too fast for anything but engraving on steel. And the structure would need to be much more massive to effectively mill steel. Wood machines need dust extraction, but steel machines need flood cooling; these things aren't really compatible.
It looks like you chose those motors for the highest holding torque possible, without considering the voltage required to make them run with any speed. At 16 mH, the inductance means that you'd need to supply 128v DC power to run them optimally, but your drives max out at 80v. If you haven't bought all these electrical components yet, I'd suggest you hold off until you decide what you're really trying to build, and have the frame constructed - things can change in the middle of a build, especially if you're learning as you go.