Need some pointers please - searched many hrs but need a shove in the right dir.

A bit of background to my question.
I have a HM-46 mill I wish to convert to cnc (also known as RF-45, PM 45 or something like that)
This CNC stuff is new to me.
I am comfortable on the stepper motor side of the hardware equation, but just need some help on the controller(computer) hardware selection.

I have read about jitter and generally understand some of the things to look out for and what to do in bios when selecting a machine to run linuxCNC.
I have also found the community hardware list of jitter results and looked through this list extensively
But Im still finding it difficult to make a decision on what SFF machine to choose in the second hand market on Ebay.
Im worried that I might choose a potatoe with horrible jitter.

I was hoping someone could point to a old SFF machine (old enough to have a parallel port)

Thanks

Thanks for pointing out your post.
I'll follow along.
Cheers