2 G i would say (i have the game i am just waiting on all my parts to start building and testing) but if you want to future proof i would say 2 G apparently FEAR can do with extra RAM and i am sure some of the games coming out in the near future. as for 2 X1 G or 4x512 then 2 x 1 G as they run with tighter timing (1T as opposed to 2T, if you dont know what this means dont worry it just means it is slightly quicker) it will also leave you with 2 empty slots for any future upgrades