I'm sorry, I misvoted. I read that you were looking at a 980, not a 780.
The 780 uses about 200W of power peak.
http://www.tomshardware.com/reviews/geforce-gtx-780-ti-review-benchmarks,3663-17.html
The TDP of a 4670 is 86W, and it looks like a system under CPU stress test using a 4670 might...