I was building a new PC for a client. The thought came across, how powerful should it be? Here is some interesting info I have found.
A PSU will ONLY use from the source what is being drawn by the system load.
A PSU that runs warm/hot draws more power.
Therefore: It is far more economical to run a higher watt PSU than a lower watt an the system components will always run cooler when there is a PSU installed that is well overrated for the system.
The more efficient your PSU, the less noise it will make, the less power it will draw, and the less it will cost. PSUs are rated at five levels 80 Plus, 80 Plus Bronze, 80 Plus Silver, 80 Plus Gold and 80 Plus Platinum, with Platinum being most efficient. If you use your PC a lot you will want to go with at least a Gold rating.
750 watt power supply here we come!