For stress testing I've noticed FFXIV does it better than any synthetic benchmark like furmark. I just have to go somewhere with trees/grass/flowers and the GPU heats up to 90C with full use. GTX560ti Hawk seems to have something against nature. Furmark gets barely to 80C if even that high.

Considering it's always different error, I would suspect HDD, CPU and RAM, as some failure in those can result in completely random errors. Graphics card errors rarely result in bsod. Of course, then there's PSU and MB that can cause the problems too, like voltage spikes etc. You don't need too big of a spike / undervoltage to get funny bits.

Can also try Linx for CPU stress testing, at least for me it's been better at stressing my cpu than prime95.