Software for overclocking Crossfire?

[Chaos Water]

Is there a safe software to overclock my 2 6850's?

 

[unksol]

Asus gpu tweak is much better

 

[DoMoose]

Asus gpu tweak is much better

I crossfired my a10-5800k with the Radeon HD 6670 and whenever I try to overclock using gpu tweak my computer just dies and the settings revert to their non-overclocked settings. Help?