Update:

>>> [...] USB2

>> All features that trump our own hardware (except for the last - IF
>> you add a PCI USB card).

> My Mac mini has on-board USB2, and so does the eMac :-)

The "silent" on-board USB2 of the PowerMac G4 FW800 is now supported by MorphOS:

"Enables USB2 mode for onboard NEC chipsets in PowerMac FW800."
http://www.morphos.de/releasenotes/3.0