My apologize. From the way Bremenacht was talking to me eg“You have no shame at all.”,
I was sure Bremenacht wouldn't make such a statement unless your system was working and they had been partially vindicated.
Reading the manual for your motherboard and cards, I'd leave the bios alone, there is nothing mentioned for crossfire/SLI bios in the manual, it should all be UEFI changeable from the driver if there is adequate power getting to the cards.
The manual says
Minimum requirements for installing a single AMD Radeon HD 6950/6970 graphics
• A 500 watt or better power supply with two 75 watt 6-pin PCIe power
connectors for the AMD Radeon™ HD 6950.
• A 550 watt or better power suplly with one 75 watt 6-pin PCIe connector
and one 150 watt 8-pin PCIe connector for the AMD Radeon HD 6970.
• Certified power supplies are strongly recommended; for a list of certified power
supplies, see ati.amd.com/certifiedpsu.
AMD CrossFireX™ Requirements
Minimum requirements for installing an additional graphics card for
One AMD CrossFireX internal bridge interconnect per additional board
• A 600 watt or better power supply with either four 6-pin PCIe power connectors
for the AMD Radeon HD 6950, or two 6-pin power connectors and two 8-pin
power connectors for the AMD Radeon HD 6970.
• For an up-to-date listing of certified power supplies, see ati.amd.com/
On the face of it, it seems like crossfire will work on any 600watts supply provide it has enough pcie connectors, but when look at the low wattage PSU in the list at 650watt, they are 80 Plus premium, and of the 750watt models I checked they are also high current models (80 plus bronze, silver, gold). Essentially anything at the normal 80 Plus level needs to be rated higher to provide adequate power.
The new supply you listed from coolmaster isn't certified, but as an 80plus bronze at 750watt with the necessary connectors it should do the job.