Since you're not a serious gamer, check out one of the midrange cards, e.g. the ATI Radeon HD 4650 or the nVidia 9600 GT or 9600 GSO. For $800 you can get an awfully nice machine...though I much prefer building my own rigs (my own rig w/o monitor cost only $600 and will easily play any of the latest games
). I personally have an ATI Radeon HD 4830, that's a bit overkill for SH3 but it's great for higher-end gaming.