I haven't seen this posted on we got served anywhere, but the developer of Stablebit Drivepool, posted over at the home server show how to enable port multiplication on the hp microserver, and if your already running a modified bios to enable ACHI for sata ports 5 and 6 (esata), your almost there.
this is awesome, now, the only issue with enabling this is that you lose the ability to use the on board raid, this also seems to apply to PCIe raid cards as well.