What is the temperature of your CPU usually?
CPU cooler doesn't affect the performance of the CPU, it just keeps it from overheating, that is the main purpose. However, if your CPU is too hot (80+ C) then you should change the cooler as the CPU won't perform as well if it's close to 100 C, not to mention you run the risk of frying it or your motherboard. But if it's around 50 C then don't bother as a new cooler won't affect your performance.