Hi UK.
The guy at Gecko is named Mariss and is truley a brillant mind when it comes to electronics and motors. What he meant by the 100/200 watt is actually quite simple when you get to understand Mariss. 100 watts or less does not need the extra cost involved of servos!
When it boils down to money I always look for the most efficent means to accomplish my goals.
Servos will give you quite a bit more torque across the speed range of the motor,,,,,,but at a higher cost, and that is the reason Mariss uses the 100/200 analogy. He deals with many diy folks and understands that cost is always important.
The G2002/2003 is basically a very high speed step generator. You will still have to have the drivers such as the 210 or the 320 which both use the step multipliers. The 2002 will not have encoder feedback capability but the 2003 will. I also believe if I remember correctly what Mariss told me is that the 2003 will also be capable of plc duties as well. You will also need a GUI or graphical user interface and the one I will use is Mach2. Mach2 is being written right now to work with the G200x series and when finished will be the finest package for diy on the market. Uh...that is in my humble opinion of course!
Mike