Mid 50's is acceptable. 60C is on the high end, but liveable.
Low 50's will give you the longest cpu life.
Have you adjusted the cpu fan profile? If not, then make the cpu fan speed up a little more between 55 and 60 C
Even a 10-15% increase in fan speed can drop temps several degrees, and get you in the happy zone for FX series chips.
Tweak the case fan speeds a little to suit.