The Wraith Stealth is a bad cooler. Try the Cooler Master 212 evo or the smaller Antec a40 pro. Thermal Grizzly Hydronaut is a very good paste.
You can use a small screwdriver to put a rice-grain-size blob of thermal paste on the CPU in the middle. Also use it to straighten any bent pins. Renew the paste every 12–18 months.