I have a n Asus HD 6770 myself, when gaming, ive never seen it go beyond 60 deg. I also live in a hot climate country, have only 1 other fan in my system. Your gpu is probably overheating. Getting new thermal will only help your cpu. My opinion would be to get more fans for your pc, and try to clean the dust from the system. Other than that im not sure what else you can do.