OK, I've got home and started to work on my system... - and have good news and bad news...
🙂Let's start with the bad ones... first thing I've tried was to look for the OC Key's firmware... well, could not find the present version of it, and also was unable to find and update... was looking on the Asus product page for the RIVE, but absolutely nothing...
😞 So, just gonna use the BIOS...
But, I also have good news! :cool: Took out the GTX680s, double checked the solderings (I had to enforce one of them on one card) and switched to the second BIOS chip on the RIVE... - and now everything is working!!! :cool:
My GTX680s were never able to reach 1250MHz on the GPUs with stock voltages, and now they're running at 1301MHz:

Yes, everything, except the graphics cards, is on stock yet... and it's just PCIe Gen2... - but at least the system start working! :cool:
Now, I'm going ROG'N'ROLL and push these cards to their limits... further result in my thread... (link in the signature)