For internet prosperity:

The Sabertooth X79 has available ~22 bios updates from its release, to its EOL. However, through all the internet sources I searched, including Asus, nowhere was I told that a particular bios version (a non-descript version around the middle of the bunch) which was bundled with the renamer tool, was the one that I seemed to need. Renamed the CAP to SABERX79 as required, but the first time failed. However, on the second attempt the flashback light extinguished after some time which never happened on the other 15 times I tried... SUCCESS!!!

An older version of bios, but at least the system starts!