Depends on the machine....
These Servo's will generate 125oz/in of torque so they are not that powerful. You'll probably use some kind of belt/gear reduction system. Most folks do with steppers since they operate at high speeds. Here are the specs on these...http://www.compumotor.com/catalog/c67_74.pdf
I'd use the encoders since it'll eliminate missed steps.
Even with the servo and encoders you still need drivers for the servos. Like one of these for each servo: http://www.geckodrive.com/product.aspx?c=2&i=14474
A standard BOB (Break out Board) will be used to connect to the PC via a parallel cable and then connect the BOB to each of the drivers that then connect to the servos. You will also need a power supply.