I am using one of those power supplies myself, and I have just bolted it to the case on stand-offs. Works fine for me. Doesn't need earthing as there is no external metalwork that is likely to come into contact with mains voltages.

I have also just come in from the garage where I have been setting up my new machine. As part of squaring the gantry, I have been checking repeatability of position of the gantry using a dial gauge. I'm using cheap proximity switches (mine cost something like £20 for 10 when I bought them a couple of years back but they are a bit suspect so I've just bought some more at about £10 for 4 although I haven't tested these yet). You can't expect wonders at these sorts of prices, but doing a set of runs where I move the gantry down the X rails a distance, then home it, I'm seeing something like 0.02mm repeatability in the homed position. However, I haven't gone round and checked things like the ballscrew bearing nuts since I first put it together and there might be a bit of play as the bearings settle in after a little bit of use. There's also a bit of uncertainty in the position as my dial gauge isn't ideally positioned and isn't as solidly mounted as it might be. Nevertheless, that's probably acceptable for a machine primarily intended for wood.