Recommendations for the most optimal PSU for this 1U system

Hey,

I'm not 100% happy with the stock PSU that comes with this 1U:
http://ift.tt/1G5RBkP
This is the MB/CPU in question..
http://ift.tt/1G5RBkR

The PSU although quite decent, has an efficiency sweetspot that's way above what the CPU will idle at.
Even when the MB/CPU is maxed out, it'll probably only just hit the efficiency sweetspot, & probably not for extended periods.

Can folks here recommend something that's FAR better all-up?

Thank-you.

Recommendations for the most optimal PSU for this 1U system