Hi,
engraversoflight is correct, refurbed XP or Win7 PC's are the cheapest way forward, no additional equipment required.
An external motion controller solution is a future looking solution. With the extra bit of hardware, the controller board itself, then just about any PC can be used
instead of the increasingly rare parallel port equipped PC's Additionally extra software loaded onto the PC is very much less inclined to upset Mach as is likely
with a Win7/XP 32bit PC and parallel port.
External motion controllers have hardware timers and produce very accurate and repeatable pulse streams which result in smoother motion. When I got my
ESS I was able to increase the max axis speeds and accelerations by one third without losing steps and the steppers run no hotter, maybe even a little cooler.
I had, prior to getting an ESS, resisted the arguments that suggested they were a better solution than a parallel port. I've changed my mind since using one. Of all
the pieces of hardware I've bought for my mill the ESS has proven to be the best value item....improvement per dollar spent.
Craig