Recommendation for Upgrading an Original parallel port KX1 to USB or Ethernet

[m_c]

That's a bit rubbish if you can't use a step/dir output to control a spindle.

Other options to look at that would be a direct plugin to a parallel port, would be the CNCDrive UC100, or the PMDX-411 (which is Mach 4 only).
If you're wanting to rewire and do away with the parallel port, there are a lot of other options.