I currently have a 20" late-2006 iMac and plan on upgrading as soon as the new iMac's come out later this sping/summer. I have 2 GB of RAM installed (1GB x 2) but I'd like to have 3GB total because I need to use Lightroom 4 and have it running at bearable speeds. Is it better to have an even amount of memory in each slot than an odd amount? Was planning on getting a single 2GB stick so I'll have 2GB + 1GB, but I read somewhere that it runs better when you have the same amount in each slot. Is that true?