I've had no trouble at all sinking ~1 ampere from a 12-volt source using ULN2003A driven from an 8748 with a series resistor of 100 ohms at its base, and through the windings of a stepping motor that purportedly drops about 5.6 volts at ~1 ampere. There's a 1 ohm resistor to VCC from the motor windings, and those drop about 5 volts when a winding is driven. The internal diodes seem to be adequate to suppress back-EMF.

The thing runs a machine in the shop and I haven't looked at the details for decades, but those numbers come, in part, from the motor end-plate and from my recollection of what I built back then. I'd point out, too, that there's a capacitor involved, which limits the duration of a given stepper phase.

RE