I have 1 pair of slots free. Thinking of just going for the gusto with 2x4gb fb-dimms. http://www.newegg.com/Product/ProductReview.aspx?Item=N82E16820148128 Seems like the best price I can find by around $30. Presently I have: 2x512mb (stock) 2x1gb 2x2gb Think it's better to try to match what I have more than go for 4 different sizes of memory? I know there's some performance benefit to having each card matching... Maybe one card with 4x2gb and the other card with 2x1gb? Input appreciated!