I believe so, yes.
ok i think I'm going to get the corsair cx 750. hopefully it'll solve it. DO you think it'll make my fps go up? and a nagging question I'm having is why was I able to run the GPU for like 3 hours w/ no probe?
I don't think PSU if of any issue now. If you said that your GPU was running fine on 3rd slot(v2.0), then problem is solved.
Don't worry for performance as it would be equivalent for both slots, but 3rd slot may have slightly lower memory bandwith which should not be a problem if you're not using a triple monitor setup or going higher than 1080p.