Durring video rendering ASUS Suite 2 says my CPU is hitting 65 Celsius, while Core Temp says none of my cores are even getting past 51 Celsius. I usually use Core Temp but I can't help but think what if there is a problem.
Yeah, as Master-flaw said you're getting two different readings, the core temps and socket temp.
Just as an FYI, for the FX series the official max core temp is 62c for the cores and 70c for the socket. If you want to view both of them you can use HWiNFO64 (sensors only mode) or HWMonitor. You can probably reach 75-80c at 100% usage and be comfortable. As long as it doesn't exceed the max temps in normal/prolonged use, you're fine.