So i'm looking to buy more RAM for my C2D 20" iMac. It currently has the 2x 500gb that came with the computer and I find it gets bogged down somewhat frequently. I usually like to work with multiple applications running (adium, mail, safari, itunes, photoshop, aperture, word etc) and I find it slows down quite a bit when I have some of these running simultaneously. Now i'd like to know which would be a better way to go. Buying 2x 1gb sticks (CAD$140), or buying 1x 2gb stick (CAD$199) and use it along with one of my existing 500mb sticks? From my searches, I realize there is an incremental performance improvement by using matching RAM.... on the other hand, if i go the route of buying a 2gb stick, my iMac would have 2.5gb ram, vs 2gb, which may or may not make up for the difference of not having the ram matched (i have no clue). Which one would you guys choose and why? Would performance 2gb + 500mb be noticeably better (assuming I'm running a lot of apps) than having 2gb (matched ram)? Thanks.