it will be safer if you use a 420Watts PSU. Since ur spec is so power hunger. I believe the start up power supply is just nice at 350Watts. But, do remember that hardware devices sometime draw a bit more voltage during some interval of the day. Another thing to note is, if ur monitor also draw power from the PSU or standalone? If its also drawing power from PSU, think, you can try using a standalone plug and see if the problem still occur. If you intend to add on another IDE device, then changing the PSU is definitely a wiser choice. I remember that i read abt the PSU using abt 50watts more to start up when you switch it on, only to go back to regular mode after it start to load the OS. Correct me if im wrong.