Yes, that PSU can cope with two GTX 760s, and your FX-6300.
Source: based on the following review, the two 760s use about 350W at most, so even allowing an extra 150W for safety for the two cards (for abnormally high loads and overclocking), it still leaves plenty for the rest of the system. http://www.guru3d.com/articles_pages/geforce_gtx_760_sli_review,4.html