Not sure what is going on with your PC shutting down. My cards will overheat sometimes but then CGWatcher just turns the intensity down and it recovers. The only problem I ever had with mining and my PC shutting down was when I was trying to use a 630W PSU. Once I upgraded to the 850W everything was fine.
Crossfire does not give any benefits to mining, so there is no reason for it to be on, and most see improved performance with it off...
Not sure what is going on with your rig though, mate. The PC shouldn't be shutting down at those temps... most cards run fine at 85-90ºC it is just not recommended to mine 24/7 at those temps unless you are like me and trying to blow up a card lol
You could try another brand, but you might not have any better results. Try sticking a box fan right by your rig and see if that helps keep the temp down.
Yeah my PC just shutdown again and temps were below 80c, could it be a sign of a failing PSU or not enough power? got 850watt OCZ gamextream. Has never happend before with just 1 GPU seems to me like not enough power more than failing PSU.
Thinking about just taking the XFX card out and using the sapphire, do I need to reinstall any drivers?
Was able to get max 510kh/s with reasonable temps both cards under 80c ran for like 5 mins and PC just turned off.