You should only need a breakout board and drivers.
If you include some more details (what kind of steppers to have now, what you're using the machine for, etc.) there might be a few more suggestions.
I'm not sure how this will resolve all of your concerns, but this *may* be a direct plug in for your UC100 and I've heard good things about this:
https://www.avidcnc.com/leadshine-mx...ver-p-334.html