Dear,
Temp under normal use of 30 and at load 40-50 is way within the limits. You don't need to worry about your CPU. As this CPU is non k version, stick with its stock cooler (Intel Cooler).
Switching to CM Evo would not give you much better temps.
Just make sure that your case has good air flow inside. you may install fans on the front side and let the heat be exhausted from the rear.
If you can provide CASE model, then I can give you better info
