I think you should definitely prioritise the spindle over the smooth-stepper. Since it's only quite a small machine you'll be able to run it perfectly well from the parallel port, so I doubt the smooth stepper will make much difference. Compare that to the spindle which directly affects the machine's ability to cut accurately and efficiently.

I'd like a smooth stepper too (as mine is bigger), but I'm not bothered when really as the machine runs perfectly well. It should just be a little more stable with one. Just going to wait for one to come up cheap...or make my own version. Whichever comes first.