People people people. Its not just wattage. You can spend £10 on a 600w power suppply and it will not work properly with a lot of devices attached. You have to look at the amps it can supply on the rails. The worst time for a power supply is at boot as this is generally the peak load there will be on a power supply
Though in the case of the seasonic I am supprised at this as they are top quality supplies. I would suspect that there is either a problem with it, or there is an issue with hardware
