Dave, Peter has a DC motor, so your suggestion won't work.
Personally I'd recommend a KBIC, however they're at least 4x the price of the ebay link.
That controller alone would provide you with speed control, however for full cnc control, you'd need to add a relay so power gets turned on/off, along with a step/dir to 0-10V converter which will most likely have to use an isolated supply. And that's only if you want single direction control. If you need to reverse the spindle, you'll need to add another relay into the circuit.
The simple option is the linked controller combined with a relay to turn the spindle on/off, and using a potentiometer to manually set the speed.