I forgot to say that in iAtkos v7 the version is Leopard, not Snow Leopard. Please note that the BIOS change is no more necessary (at least for me) since I'm using iAtkos.

UPDATE:
Now after having connected to the internet with the USB Key, I updated the software from the Finder menu... Some updates were fine, the last one, labeled Mac OS X updates or something similar (200+ Mbyte), had a devastating effect on my previous install: screen reverted to 1024x768, no USB hotplug, and only God knows what else ... keep in mind this before you try updates. Seems like the whole Extensions folder has been overwritten by the update.
Patched the screen again, now it's ok. Need to reinstall the USB driver and (perhaps) the newest kernel mentioned in my first post, but my dvd is at home...

REMAINS UNRESOLVED: the network card (wired and wireless) not working yet. I've just downloaded a driver named AttansicL1Ethernet_10.5.6.zip but haven't tested it. I'll post updates later, in case of success will give you the path. No. Not the good one.
Next step: I've found there's an Universal Network Driver for Mac OS project in sourceforge.net, I think I'll try it, even if it's in beta.
Stay tuned!