I'm getting a bit closer, but a little confused.

I think the ESS-MB3 does what I need stand-alone. Just plug all my hardware wires into the right spots and set up the software. Unfortunately, a bit pricier than I hoped and currently out of stock.

My comment about ethernet to parallel was based off looking at the wrong image. I saw a UC100 metalmayhem warned about and that does look like it just plugs into my existing parallel port and on to the existing BOB, which doesn't do what I want right now, as my existing C10 bob doesn't get me spindle control.

The UC400ETH seems functionally more like the ESS-MB3, but it also looks like it runs through a ribbon cable to plug into an existing bob? Am I getting this wrong?

I also see a UC300ETH which seems to have the capabilities I need, but all of the connections are ribbon cable connections, so I'd need to add ribbon cable breakouts, unless I'm missing something. I just have a bunch of wires screwed into the current bob. No ribbons.

Thanks for all of your help!
Mark