Many thanks Lee. I have to say I've put off buying drivers for some time now due to utter confusion about what I need.

My machine is a small professional milling machine with ball-screws and a table with axes weighing round 50kg each. The Astrosyn L709-2 motors exceed the torque of the old motors and I have no intention to upgrade further. Being a metal machining tool, I'm looking at relatively low feed rates.