The options under the overclocking section of the bios only lists the following for Voltage ; PLL1 and PLL2 Spread spectrum is listed only for enable/disable. Are you able to point me in the right direction Ski?

Processor-NB Voltage
NB voltage
SB Voltage
CPU VDDA Voltage

I am going to have to play with it to see the point as to which I lose x-fire.

I am not overly concerned as in the near future I plan on getting myself a single card solution. Played with the thought of two 4470's - for price, heat, power consumption and performance - but thinking one 4890 is the way to go.

Better performance, and the same if not cheaper right now than two 4770's in xfire which will only get cheaper in the coming month or two.