I remember few years ago that the early 2008 iMac can handle 6gb RAM, instead of maximum 4Gb that Apple says. I don't mind in that days but now i reconsidered it. I use Logic and the extra RAM it's very valuable. You must put one 4gb bank and other 2gb and you get 6Gb fully working. The price of 4gb single bank it's more affordable in this days. I bought one Patriot 4gb module for 100€ on Amazon Spanish store and now my iMac it's fully working with 6gb (recognised and used). If anyone is interested, this is the exact module that i bought: http://www.amazon.com/Patriot-Signature-PC2-6400-Notebook-PSD24G8002S/dp/B0027IVMBY it's more cheaper in the US Amazon.