Looks like we both came up with the same research, it looked like it would work to me too, I did a bit of reading on it and it does seem like it would work coupled with the sprint board.
The only other possible solution I came up with was coupling the UC300 ETH 5 LPT with a cheap Opto isolated bob with analogue outputs into the sprint. its a much more expensive option but would serve 2 purposes - 1. as a motion controller and replacing the parallel port with Ethernet. and 2. As the spindle speed control board. From what ive read it would work, but i havent gone that route yet myself so do your reasearch dont take my word for it!
I'm someone will chime in and tell you a better option now ive mentioned it though.