Your problem is GPU related, as in the GPU isn't getting proper power when stressed by game play. The underlying reason is that although the Strike X psu looks cool it isn't a good performing psu, they have issues. The psu is of low quality is going to cause stability problems with your system. Below is a full review of the larger 800W Strike X.
http://www.kitguru.net/components/power-supplies/zardon/aerocool-strike-x-800w-psu-review/7/