The power supplies are available in various sizes and wattage. The power of your power supply depends on the sum of the consumption of the components you have in your PC. You have the choice between a fixed wire feed, this means that the power supply has all the possible cables already connected, so you certainly will find the necessary cables. However there will be other cables that you will not use. The modular power supply gives you the choice of cables you use. The cables required will depend again on the type of components you use inside your computer.