Hi,
You may be going about this the wrong way.
You need to determine what type of spindle you need. Price is not what you use to choose the type of spindle. Price is used to choose within the range of a particular type.
A High Speed 2400W Chinese spindle is a completely different beast from a 200W DC spindle. The Wolfgang TB 650 spindle is basically a PCB or engraving style milling spindle.
What type of milling are you planning to do, wood, engraving, etc? These two spindle would normally suit different sizes of machines.
The wolfgang 12V spindle has no speed controller. It connects directly to 12V.
Mach produces a PWM control signal that is proportional to the requested speed as a ratio of the maximum speed. This control signal need to be processed and interfaced into s speed controller.
For a VFD, you could use a DC-03V3 Digispeed to accomplish this.
http://www.homanndesigns.com/store/index.php?main_page=product_info&cPath=1&products_id=21I'm not aware of a 12V motor controller that accepts a PWM control voltage.
Cheers,
Peter.