If you want cheap, easy and fast, look at www.xylotex.com for a 3 axis drive kit with steppers. Every thing you need is there.
For table movement on a machine that small, you might very well get away with 1/2-10 acme, if you could shield it against the plasma dust, but my recommendation is to just use some timing pulleys and belts for gear reduction, and then use some 20 degree PA 20 pitch rack and spur gear.
Here are some inexpensive pulleys and belts. Always had good luck with this guy.http://stores.ebay.com/HUBBARD-CNC-I...QQftidZ2QQtZkm