|How do you know one of your DDR2-667 sticks was "broken"?|
This new combination has knocked the memory out of dual channel mode. So to answer your question, 2 x 1GB in dual channel mode is better than 2GB in single channel mode. However, 3GB in single channel mode would probably be even better. You *should* be able to run both the 1GB & 2GB together but you may have to experiment with the way you have them configured in the slots.
It would help to know your system specs. At least the motherboard make/model or if it's an OEM system (Dell, Gateway, HP/Compaq, etc), the make/model of the PC itself.