Gam3r is correct, the stock heatsink will keep it cool if you keep it at stock (hence the name).
I would recommend picking up something like a Cooler Master Hyper 212 plus/Evo, as you will get 10 - 20 degree differences from the stock cooler, and is more quiet as well, in the future.
The temps would be around 75c - 85c, and 90c under prime95.