Power Supply Requirements
First of all: forget generic power supplies! The current requirements for systems based on Prescott CPUs are far greater than previous Intel processors. The power supply must be capable of providing at least 16 A at its 12 V output and no generic power supply can provide this current. Usually generic 400 W power supplies are capable of giving 12 A at its 12 V output, at most. Using a generic power supply with Prescott processors can burn outr the power supply in just a few months, risking all the system.
Figure 5: A 400 W generic power supply, innadequated to Prescott processors (this particular model can only supply 10 A at its 12 V output).
Thus it is adviced to use a power supply with at least 250 W true power from a known brand like Seasonic, Seventeam, Zalman, Emacs, Enermax, OCZ, etc.
For systems with high-end video card and several hard disks it is good to think on power supplies with 400 W true power or more.
At https://www.intel.com/cd/channel/reseller/asmo-na/eng/tech_reference/35815.htm you will find Intel list of tested and approved power supplies for Prescott-based systems.