I have an old (probably Vintage!) 2.5A Routout CNC controller box running my little CNC mill, I added a 4th axis using a Chinese board and while this got me up and running the Chinese board got a little jittery when I turned the Flourscent shop lights on, powered up my manual mill inverter drive, or looked at it sideways ;-)

I found Routout CNC were still trading and gave them a ring, their technical chap located a matching board for me and 2 days later I have a fast, smooth, stable 4th axis ready for all the 3D jobs I've completed the CAd/CAM for!

I checked the website and their prices are good, especially when you consider the quality & service and that they are UK based, I think they offer far better value for money than Chinese stuff off ebay given the massive reduction in setup time,

- Nick