Actually I have a CNC3040 but it looks like the 6040 uses a similar motor controller given the enclosure size. I'm new to all this so I may be wrong but I suspect the motor controller is the weak link. It looks like it is an all-in-one 3 axis board like the CNC3040 uses and it runs on about 24 Volts. If you look at the driver circuits from ZappAutomation and the like they run on 50-80V. The motors are of course also a consideration but I guess just going by the size of them, they could take a bit more power.

Someone please correct me if I am wrong.

Also, given the response of the people I purchased my unit from, it seems there is a central manufacturere and most of the items on eBay are from resellers. Does anyone know who the original maker of these designs is? Is it www.cncdiy.org?