I've read many of the threads regarding RAM pricing and configurations for the 6-Core systems. I planned on ordering my Pro with 6Gb instead of the default 3GB, but my friend at Apple forgot when he placed the order. From what I understand RAM module placement and type may significantly impact system performance for this platform. As I need to double the RAM, should I purchase 3x1GB modules to add or purchase 3x2GB models and sell the 3x1 that came with the system? Also, which is the best RAM retailer, OWC, Crucial, etc? Thanks!!!