I don't have it any more so I can't test it to see, if fully working unit can have other PSU and still work fine with 3 hashboards.
Yes it can, I just tested it, 2 boards connected to APW++ and one board connected to DPS-800GB (HP 1000w PSU), and it works like a charm on full speed.
Oh. That's great to hear. So it was mine unit, which could not work efficiently with 3 hashboards on, no matter what.