X7DWA-N 550W PSU recommended?

I'm looking at this mobo:

http://supermicro.com/products/motherboard/Xeon1333/5400/X7DWA-N.cfm

I'm just curious why does it require a 550W PSU minimum "To ensure
system stability"? If I put 80W 54XX Xeons, it totals 160W, and I
doubt with all the other devices (8 SATA drives, graphics adapter, CD
ROM, etc.) will come close to 250W. Then
why on earth would they require such a highend PSU?

 

The SM X7D series of Mobo's are all Server/Workstation boards. Between the
Chipset and the onboard acc you have a BIG potential for power drain from
most systems using this board. I have 7-500GB SATA HDD's plus a 1-160GB
Raptor SATA HDD in my SM chassis with a X7DAL-E Mobo. Add two Video cards
and you can see where the power need comes from. Place this Mobo in a SM
SC743T Chassis and there will be NO issues with a PS…it comes with a 645W.
Other Chassis in this set have over 800W PS!
Hope this helps.
DER