Yep you need to invest on new aftermarket HSF. A cpu with a hsf should be idling at 35-50c depending on the ambient air temperature. Find a good hsf through reviews and as well as a good thermalpaste. Keep in mind that you also need to have a good ventilation in your case and that it's taking plenty of cooled air and exhausting it as well. This is very important otherwise a hsf won't be able to do it's optimum cooling performance without a good supply of cool air. Place a fan on the side panel for example and point it to the hsf to get more cool air.