I get one short beep out of my DG45ID when it boots - from the tiny tweeter built onto the board.
As for the PSU issue, there's a setting in many modern BIOS's to go to the same power state the PC was in after a power cut. Turning the PSU power toggle switch off makes the motherboard think there's been a power cut so when power comes on again, the PC has to momentarily get things ready again. What you describe sounds normal to me.
Both the beeps and the system coming on for a couple of seconds is normal.