I'm looking forward to upgrade more memory into my dell dimension E 520 system. after some research, i know that i can update from 2-4 1G DDR2-667 (PC2 5300) memory ram. But is there any specific thing that i have to look into buying the ram? like if there is good brand vs. bad brand? durablity, etc? where (online) should i buy? any reccomendation? i dont know much about this stuff so just wanna have a double check. thank you very much.