Hello, I just got a 2011 iMac (I chose not to wait). I followed the advice of getting only the 4 gigs of ram with the plan to upgrade aftermarket ram. I've been looking on amazon. My question is, which is the best ram to buy and how much should I get. Also, I currently just put 15000 photos into iphoto. When scrolling, it's super choppy and doesent respond well. Is this a ram issue?