To answer your configuration question about encoders, most hobbyist CNC machines are open loop. They don’t feed back the position to the controller with encoders.
The equipment ZASto suggested should be a bit better that what you have but has little extra for adding more features. Also you will need a power supply for the steppers. The stepper drive photos show they can use 9 to 42 volts. The higher the voltage, the more torque and speed you will get from the motors.
Here are a number of things to consider before you select your new equipment. I am including features you may want in the future. There are many posts discussing
specific pieces of equipment.
Type of Interface to PC BOBParallel - 1 port, limited number of Inputs and outputs.
USB, Ethernet - Multiple ports, some have an External motor controller
http://support.machsupport.com/en/kb/articles/what-is-an-external-motion-deviceElectrical Isolation from the PC protects circuits from damage and interference. Isolation between the interface and the steppers and spindle is important too. The drives in ZASto’s link are optically isolated.
Many interfaces need a power supply, usually 5 volts.
Equipment to be interfaced Limit and home switch inputs – more IO ports allows separate input of switches to help with troubleshooting.
E-Stop input
Stepper motor drives
Relays for Spindle On/Off - direction, Coolant, etc
Analog output for spindle speed
Stepper motor drivesMotor current, speed
Stepper motor power supply
Current setting for your steppers – we will need to determine that later
Optional equipmentProbe – set tool height
MPG – manual pulse generator to manually move the axes
LASER