Looking at my machine whilst wiring up the closed loop steppers and cursing the Chinese bods who don't use screened cable for the motor wires - WHY??? -there's 48V switching edges on those wires!!!!! - I suddenly thought why not put the driver modules on the machine next to the motors? That way all you have to run from the control box is low powered step/direction/enable lines which could easily live in a a bit of 26 AWG 6 core screened cable (about 4.5mm diameter) connected by M12 connectors and power which could be a few strands of 1mm2 wire twisted together*, or if you're flash some high power flexible coax like the Mogami 3082.

* actually 2 x 2 x 0.5mm2 would be better on reflection.