Mach3 to DC Servo conversion

I use DC servos with optical encoders on my mill through a step/dir interface on each axis. Currently, I use the USB Smooth-Stepper hardware to interface the PC to my servos axis controllers (which works very well) however, with a processor running each axis, it seems a shame to be wasting it on processing steps and direction pulses.

I'd like to create a plug-in or interface code that allows me to send Mach3 position, speed and direction information directly to my controllers without going through the step-direction hardware interface. Whether through serial like MaxStepper, or USB like Smooth-Stepper, I don't mind which comms interface.

What does Mach3 send to devices like SmoothStepper that encodes the information that I can send directly into my controllers?
How do I get access to that type of real-time information? What drivers would I need to write? What can I expect from Mach3?

Any help would be greatly appreciated!
-Robert