This is the configuration I bought: 20in 500GB HD 1.5GB RAM However, I was thinking of changing to only 1GB of RAM. I know you're supposed to get better performance out of your RAM on the iMac if your RAM is matched in equal pairs. So, what is better? To have: 1GB RAM 2x512 GB in matched pairs -OR- 1.5GB RAM 1x1GB + 1x512GB Really undecided here. Educated opinions weigh in please! Thank You.