Mike
"I have decided to go with the parallel BoB and spindle board and LinuxCNC"

If you go with 2 PP boards in a PC you would also be able to change the two pots (feed rate & spindle speed) to encoder pots and have them control the sliders on the gui in linuxcnc.

I have done this but using a mesa 7i92 (if I was doing it again i would use a 7I96). These get rid of the PP cards so are connected to the pc via cat5

Good luck with the build.