The case and cooler should easily handle that system , so my guess would be that you have too much thermal paste between the cooler and the cpu .
ONE tiny drop is all you need . Its to fill micro pores too small to be seen , not to add a thick heavy layer .
Also check the cooler is seated properly . If you can feel it moving then its not on firmly enough
EDIT: if all else fails try using the stock cooler , with the pre-installed thermal paste