Other Thoughts: I bought this as part of a bundle with a Sempron 3850 to power a new "headless" home server running Ubuntu.
In the process of setting it up, I found that it would hang or drag during boot when I had drives connected to the integrated ASMedia provided SATA ports. Sometimes the problem happened during device detection, other times, at the screen just before getting the option to enter BIOS setup mode.
After some experimentation, I found that the problems could be avoided by disabling CSM (Compatibility Support Mode) in the "Boot" section of the BIOS setup screen.
Once I finished configuring and testing the system, I shut it down, detatched the monitor, moved it to a closet and booted it. Rather than working as expected, it gave 5 beeps and then seemed to hang. According to ASRock's support site, 5 beeps means a VGA card wasn't detected (I'm using the integrated GPU). After more troubleshooting I've determined that when it doesn't find a monitor attatched to one of the motherboard ports, it looks for a graphics card. At some point, it also re-enables compatibility support mode.
It seems then that this board is ill suited for use as a headless machine. I'm not sure what I'm going to do about it, but it is incredibly frustrating.