According to the Aopen site click here your motherboard uses PC2100 memory, and supports Dual channel.
The Dual channel means that you should use two modules on equal size, one in one of each channel slots, for best performance.
The site says nothing about supporting faster RAM than PC2100.
What does the motherboard manual say?
The spec says also that it supports ECC RAM, which although more expensive, means Error Checking and Correction - usually used in servers and other critical systems, but a "good idea" in any system.