Are you sure it the Gpu causing the crash, could be the Cpu cooler ???
If not maybe you have to much hot air in the case, improve the cooling in the case add a couple of these
case fans not cheap though they are very good at removing hot air and also are silent - I am running 2 of these
Noctua Fans
The NF-S12 is the first fan employing a novel rotor which was developed by the Austrian Institute for Heat-Transmission and Fan Technology. Thanks to the special optimisation of the blade geometry towards ultra low noise application, the NF-S12 is up to 10% more quiet than current high-end fans at the same flow rate. The NF-S12 series are equipped with a magnetically centred, self lubricating oil-pressure bearing that provides a new level of quietness and long-term stability.
- 12v performance - 1200RPM, 17dBA, 48CFM
- 7.5v performance - 600RPM, <6dBA, 24CFM
- 3 and 4 pin power connectors
- Ultra-Low-Noise Adaptor (U.L.N.A.) included