www.candcnc.com For small to mid size machines look for the dragon cut series.
This is certainly not the cheapest but most likely the most complete & simple hook up out there. Not all that expensive either when you really take time to compair apples to apples when piecing a system together.
I like "V" rail on plasma simply because it tolerates a dirty environment better than most any other.
If you use a dual motor drive for your gantry you will need a 4 axis drive system