Newbie question: Motor sizing

Hi Group. Just joined a few days ago. Read 99% of the postings from
May. Whew. I'm already 200% more knowledgable. I'd like to build a
3 axis CNC using a Jet JMD-18 benchtop or similar. It has an approx
9.5" x 32" table. I see that Microkinetics on their "CNC Express"
puts 470 oz/in motors on the X & Y axes with ballscrews. At first
I'd like to run with the standard acme screws and was wondering what
size (torque) steppers do I need? I'd like it to be middle of the
road on speed and capable of machining materials from wood to steel.
I assume it will get faster after eventually converting to
ballscrews. Thanks.