Hi Jeff,
The -DE option is always best to have. If you don't have it, you usually have to re-home.
In either case, the easiest way to interrupt power is on the AC side of the power supply. If you have a problem with the motor still moving as the power drops out, you can use an I/O on the motor to detect that the E-Stop was pushed, and halt motion(you can program an interrupt for this).
If you need to break power on the DC side, you need to have a Shunt wired in the circuit, so that the Shunt stays with the motor, not the power supply.
If you have a high inertia load or rapid starts and stops, the Shunt is a good idea even if you are breaking power on the AC side(just to protect the motor from it's own BEMF).
-Chuck