Power Supply Unit (PSU)
Power Supply Unit (PSU) is a very important component of any computer system. It provides power to every component inside a PC. It is therefore important to choose a power supply unit that provides sufficient power for your particular PC setup. Most budget cases come with power supply unit but most of the better quality cases don't come with PSU which has to be purchased separately.
When choosing an ATX power supply unit its a good idea to get one that provides slightly more watts than you need. This gives you the flexibility to add more hardware in the future. Having an under powered PSU can also lead to an unstable PC.
If you are building a pc with a minimum specification with lower end CPU, less demanding graphics card, 1 hard drive, 1 dvd-rw drive then a 400 watts PSU will be fine. If you are building a mid range PC then a 500+ watts is recommended. If you are planning on building a higher end PC or a gaming PC with a top of the range 3D graphics card then a 650+ watts is recommended. Other things to consider is how many connectors are provided such as the number of sata power cable, molex cable etc and how much noise the unit produces.
Recommended Power Supply Units:
Cooler Master eXtreme Power Plus 500w Power Supply (RS500-PCARD3-US)
Corsair Builder Series CX 600 Watt ATX/EPS 80 PLUS (CX600)
Corsair Enthusiast Series TX 750 Watt ATX/EPS 80 PLUS Bronze (TX750)