Hi there!
Philip, I'm pretty sure Osiris means that his devices will only charge while the PC is powered on, not just the PSU (I hope). For the record Osiris, you need to do two things, one make sure you have the AppCharger downloaded from here
http://www.asrock.com/feature/appcharger/index.asp and take note of the footnotes which state the following:
The charging capability may vary with different power supply design. The more +5V standby current provided, the better charge efficiency you get.
** Please connect the devices to the PC USB ports before the PC enters S1/S3/S4/S5 mode to enable a fast charge.
*** To support APP Charger under S5 (Shut Down),
A. If you could find "Deep S5" in BIOS SETUP, please set the option to [Disable].
B. If you could not find the Deep S5 option, please set BIOS > Advanced > ACPI Settings > "PCI Devices Power On" as [Enabled].
By following those steps you'll be happily charging your phones with the PC shutdown. Just make sure to leave it switched on at the wall and at the PSU though eh?