The site linked below recommends a 500W for the GTX 670. If it is a high quality 500W like a corsair, then yes, you will be fine. Since you do have the k version of your cpu, and a z77 board, I assume you also plan to overclock? If so, personally, I'd up to at least 600W. Some will say overkill, but that's what I'd do. (I have a 750W powering my system similar to yours).