Ok I just got another reply from GGTS and it is confirmed that the GA-MA790X-DS4 motherboard does NOT support the new AMD Phenom ii X6 processors.
This is the official reply I received from the tech:
Sorry for mistaken. However, it's confirmed that GA-MA790X-DS4(rev. 1.x) does not support 6 core CPU due to hardware limitation, if there's any mainboard support 6 core by BIOS, we would release BIOS, however, the board GA-MA790X-DS4(rev. 1.x) can't support 6 core CPU by BIOS update.
This kinda su**s for me but doesn't matter.
Once again thanks for the help and support guys.