It would depend how many H-boards are in use. A starter kit would work fine with a 350W supply, even a 200W supply likely. A full 400GHash rig would need at least 500W (assuming that bitfury is operating near the 1w/GHash design), but a 750W supply would be best
That's not true in regards to the 400 Gh rig power requirements. Please read post #973 https://bitcointalk.org/index.php?topic=251966.960
arorts,
you can point directly to post #973 copying the link with post number on post header (right click on it and then copy).
https://bitcointalksearch.org/topic/m.2887512
spiccioli