If you really want cheap, you could bodge jumper wires onto the existing driver board to use the original stepper drivers, but in all honesty, they're rubbish. Fitting modern drives is the way to go, as they'll give far better performance, even with the original steppers.
If the existing spindle driver is working, then you'll need a 0-10V supply to control it, along with an enable signal.
The PSU in it should be 36V along with a 12V tap for logic supply. 36V is plenty unless you're really trying to get every last ounce of performance from the steppers. Unless you go for industrial controls, you'll be looking at also needing a 5V supply.
Avoiding the rubbish customer service from AluminiumWarehouse since July '13.