AdamTrans, have you tried the Matrix fans at full blast? Also, pay attention to the back of the card... for optimal cooling you need good airflow over there too...
You can try giving a look to the thermal paste, but if the temps are going down when you're increasing the fan speed, then i would say that your card is working properly... if you remove the stock cooler, be prepared to apply new paste... (I found that the paste used on the Matrix cards seems better than on other Asus products...)