For testing of this Arctic Cooling Fusion 550R PSU, I had used the latest motherboard monitor software to monitor the voltage. I have taken the low, average and high voltage of each rail. As for the load testing, there was a slight drop for the +12V rail. The overall performance of the Fusion 550R was very good and stable during the high loading condition. During the operation, this PSU is running quietly, almost can't hear the fan noise. Besides that, after power off the PSU, the fan will still running for about 5 seconds to cool down the components inside the PSU, this was a good features.