I would go to USB instead, because most USB controllers doesn't have the deficiences of parallel port (interrupts and limited speed).
For free you can try CNCdudezUSB (http://www.cncdudez.co.uk/cncdudezsoftware.html)
next (as price) will be USBcncController (http://www.planet-cnc.com/)
and next (that I know) is EdingCnc controller (http://www.edingcnc.com)
Hope it helps you!