Regarding the size of PSU, I had 3 module Asic running for a week with 750w PSU. After that the PSU died (it was almost new).
Now, I know some people here have been saying that 750W is too small PSU, even for the 3 module unit. Clearly that is the case, I just couldn't believe it. So be mindful of this when choosing PSU's.
750W is OK.
From time to time hardware breaks, especially when running near max specs continuously.