Controlling +/- 10V Servo Amps

http://www.electrosales.com/warner/New%20Product/tdc.htm
There are a couple of those brushless servo amps being sold on ebay.
I'd buy them (and a compatible motor) but I have no idea how to get +/-
10V out of a pc's parallel port. I'm pretty sold on the pico-systems
pulse-width mainboard, and you can get step+direction straight off of
parallel port pins- but how would either of those be interfaced to the
+/- 10V standard?
BTW, thanks for the help explaining backlash issues when I asked about
that a few threads back. I'm going to take everything apart and
hopefully track it down that way.
Michael Larson