Hi King Diamond. First I think you have got a bit confused about the voltages. Practically all modern computers use the ATX standard power supply and this defines the voltages. These are +3.3V, +5V, +12V, -5V and -12V. The difficult part is to decide what the current is from each voltage. (Power = volts x current). The power supplies usually tell you what is available at each voltage, but the device makers rarely tell you what they need. AMD try to be helpful by telling you what an Athlon takes, but in a very complex way. As a result most amateur builders rely more on guess work and experience. I would say that any Athlon above 1G clock speed should have a 350W supply, and above (at a guess) 1.5G, I would look for 400W. With a good quality supply you can usually get away with a lower rated supply than if you get a budget unit, mainly because good supply regulation and heat sinking costs more to make.