Should be enough. The 6700K has a TDP of ~95W, and the 980 Ti has a TDP of 250W. TDP is not an accurate measurement of power draw, but it is a useful approximation. So, the core components of your machine pull 345W, leaving over 200W for hard drives, LED's, and so forth, which is way more than enough.
Quality is more concerning than wattage. If your PSU is one of the cheaper EVGA units, like the ones that only have 80 Plus rating (no Bronze/Silver/Gold/etc), it is very likely to contain some very cheap components. As a result, the PSU is more likely to give out on you sooner, and it could damage some of your other components. If you have the kind of money to get such a powerful machine, I'd suggest making sure your PSU is also of good quality.