I am only able to push my GTX 670 FTW to +75 core clock and +100 memory clock. I cannot go higher. If I try, say, +100 core clock and +200 memory clock I get a display driver error and the Unigine Benchmark Screen goes black. I have heard of some people getting +200 core clock and +550 memory clock which is much more than what I am getting. I have the voltage at 1.175 V and the power target at 125%. I am hoping I didn't just get an unlucky card. Any help would be appreciated.
You may have a GPU that doesn't go as high as others. It is the luck of the draw.
However, the FTW edition is already overclocked significantly. Make sure you are comparing it to other cards with a similar factory overclock before assuming that yours won't go as high (don't just look at the core speed offset, look at the actual core speed attained). Also, case cooling is very important with Kepler cards, so make sure you are well ventilated.