Step/Direction Spindle Speed Control

www.Rutex.com has a new board "A RT990A based servo drive. Up to 200
Volts and up to 40 Amps continues current, single servo drive for
brushed DC permanent magnet motor with feedback from encoders.
Accept TTL/differential encoders @$199. This is enough power to drive
my mill's 4hp spindle if I choose to derate it a little. If I mount a
low ppr encoder on the motor shaft I should be able to use this board
with step and direction control to get about any spindle speed I
want. Great for tapping and could probably be adapted to a lathe.

Any suggestions as what to use for a digitally controlled variable
pulse rate generator to make this work? I don't know if an
inexpensive PLC would do it and I haven't had a need (yet) to get
into programming basic stamps.

Roger

PS. Or I could wait for Marris' step/direction to +/- 10 volt board
and use my existing amp. The issue is still the same.