[DonRotolo]

Be careful underspecifying a power supply. Voltage sags can cause weird things to happen, undesirable things. HDDs consume a lot of power at spin-up, and a board can draw more power than nominal for a brief time at power up.

On the other hand, the manufacturer doesn't care if you need to spend more on an overspec power supply, their best interest is in making sure the system is rock-solid stable.

My 2 cents: 200 Watts it is. Remember, 200 is the max it can supply, not the nominal consumption.