Hi,
my machine run ons a dual core Atom mini-ITX single board PC with on-chip graphics. It wouldn't 'pull the skin
off a rice pudding' yet it runs an Ethernet SmoothStepper and Mach4 very well.
The only time I notice the low power of the CPU is when I go to load large files, say 5MB or bigger. It takes quite a while to
load and draw the first tool path, thereafter its fine.
Mach4 is not a hungry program, even a very modest PC will run it fine. Don't waste money on a 'you beauty' PC, you'd be better
off spending a bit more on that next spindle....or tools....or servos...or ballscrews ...or....
Craig