I get to 55C under Prime95 load (100%) on the CM Hyper 212 EVO (dual fans), but I have a much higher end case and its freezing where I live.
Your temps arent that bad, I would say 40C is a bit high for what is essentially idle, but your load temps are fairly fine. As long as the CPU doesn't go above 75c under Prime95, you dont have an issue with temps*.
*The 2500K has a TjMax of 90C, past that and the CPU will degrade its own performance to stop from overheating. That is the maximum temperature that will technically not damage the CPU, but I personally don't think you should go above 75c.