eXtreme Power Supply Calculator v2.5
 

What power supply do I need ? To answer this question we came up with a tool that determines the overall computer power supply wattage as well as amperage required for +12V, +5V and +3.3V rails for your desktop computer, server, or any pc computer system that uses ATX power supply. Calculator contains some usefull options such as CPU overclock, System Type, System Load and more. It contains 750+ CPUs including latest Intel and AMD processors and latest video cards from NVIDIA and ATI.

http://www.extreme.outervision.com/psucalculator.jsp