Like myuusmeow said, as much as I love the PSP, its absically a piece of sh!t unmodded. You cant run ISOS, CSOs, homebrew, etc... and thats all a PSP is good for. (IMO) If youre sure youre not going to want to mod it (I dont see why not...) then just buy a 1Gb stick. That will be MORE than enough. Unless you have a lot of songs and you dont have an mp3 player or iPod, then I guess get a 2Gb or 4Gb according to how much music you have.