You should DEFINITELY have some fans on your case. Bare minimum if possible an Intake at the front to suck in cool air and an Exhaust fan on the back of the case to suck warm air out of your case. I would not be putting a 670 in a case without proper ventiliation/cooling.
What case are you using and do you have the option to add fans to it? Your current "fans" are there to cool what they are attached to(CPU and PSU) They aren't for cooling your case.
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