Here some input if you are searching for a good PSU for your MIDIbox NG(s): since one month I’m using a cheap switching power supply from Pollin (price: 4.95 EUR) on my MIDIbox LC and it works without problems.
More infos can be found here:
http://www.ucapps.de/midibox_lc/midibox_ng_switching_psu.pdf
I guess that up to 3-4 MIDIboxes with Motorfaders can be powered from this PSU.
Best Regards, Thorsten.