100C is too high, however, before jumping straight into a new cooler, you could try reseating the cooler you already have, sometimes the thermal paste isn't applied properly or is getting old. Another possibility is that the fans in your case aren't speeding up to remove enough heat. Not knowing your case and case fan setup limits advice on this side of things. I once knew someone who positioned their fans backwards, they were drawing air from the back exhausting it through the front, not the biggest error on the planet but it can make a huge difference in the thermals.
I'm just saying before throwing money at a problem make sure other possibilities are addressed.