And with that post i've been promoted!
looking at that article, getting a 2 x 1gb kit means 2-3% better than 4x512 - in some games. Also, they set all their sticks (4x512 or 2x1024) at the same timings, and you have to spend a fair bit to get 2gb kits with better timings than my value RAM, so I wonder if it would actually make any difference going 2T as I'd keep better timings with another 2 cheapo sticks. hmmm.