This is annoying as I was told I would not need to adjust that stuff with this specific card, I did however once up the "power control settings" by 20% in ccc as suggested, this caused my computer to crash immediately. Also I don't intend to go "big" on the overclocking, a 50 - 100 increase in the core clock cannot be considered big, can it?
It is not only big, mate. It is extreme, beyond the limits. 50-100%, even the best enthusiast would have trouble getting such good frequencies and I would bet even if they got there, then it would not be stable.
I usually overclock 15-20% on both memory clock and core clock depending on the GPU I use. http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/53456-gigabyte-hd-7950-windforce-msi-hd-7950-twin-frozr-iii-review-19.htmlhttp://www.pureoverclock.com/Review-detail/gigabyte-7950-windforce/17/
Have a look at the at these reviews of the Gigabyte Windforce 7950, your overclocks are very high compared to the reviews and the GPU can't really deal with such high frequencies unless you really know your sh*t.
However I've seen core clock of 1224 MHz on the GPU you got, but with the highest voltage. It is playing with the fire and I would not recommend it. It will either shorten the life span of your GPU or kill it.