The only temp that matters is the Max core temp. AMD's website specs are woefully poor so they do not list a Max. CPU temp for the Athlon X4 750K that I can find. Typically the Max 24/7 temp for these CPUs is in the 61C-70C range.
I personally prefer Core Temp software as it only list the CPU core temps and not other confusing mis-labeled temps.
Building a reliable PC involves more than just assembling the parts. You need to be able to configure all of the BIOS settings appropriately. This can be quite involved and frustrating as it can require a lot of trial and error with stress testing. It is however often the only means to get a 100% reliable PC.