|Depending the exact power supply, how many 12 volt rails (one only is best), and how much amperage is on the 12 volt rail(s), it could very well be underpowered. |
There is also the slim possibility that the fourth core was locked down because that core was faulty and could not be sold as a quad, but about the only way you will be able to be sure would be to try a better power supply.
To be more sure, please post the Amperage ratings on each of the different voltages as it is printed on the label of the power supply.
But the two power supplies I was able to find with that name both have dual 12 volt rails and inflated amperage on the 5V and 3.3V rails to inflate the overall wattage ratings. This is a trick used on cheaper power supplies to make them appear they have a higher rating then they otherwise would have and be able to sell them for more money. If they left the 5V &3.3V rails alone then it would probably be just a cheap 400W power supply and you would have passed up on it. It appears you just need to purchase a decent power supply and you should be fine. Look at this one:
Notice the 44Amps on the single 12Volt Rail, the 80% Bronze rating (efficiency), the active PFC, the solid state capacitors, and the 5 year warranty. Those are signs of a quality power supply.
You have to be a little bit crazy to keep you from going insane.