I have an i5 4670 (not-k) with the stock cooler. I just re-applied a Thermaltake thermal paste ( not the best one, but it's the only one that was available to buy in the store). The temps at IDLE are around 40°-50° C ( 50° when I have many tabs in Google Chrome). I'm pretty sure I applied the thermal paste right, so I don't really know. In my room the temps are around 25° C, in my country we are in summer.
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With my stock cooler I would get ~65C full load. It looks fine to me, but I would get a Corsair H55
Try running something which gets the CPU up toward 100% for a few mins, then see what the temperatures are. As long as it doesn't go over 75°C under full load, don't worry about it.