Just received a reply from Gigabyte regarding the BIOS:

Hi,

The standard specification for this model memory clock is 775MHz and core clock is at 950MHz. The standard bios released by ATi had this limit, there are tools available online which can bypass this. We can't make a special bios to increase this range because this would jeopardize the stability and usage of our VGA cards. We can’t guarantee any results due to overclocking.
No help from Gigabyte like there has been from Sapphire