I always end up buying a gfx card for just one or two games, last time it was hl2, then before that farcry, the flow of pc games over the past few years has been slow to say the least, good ones that is. But when a good one comes along I honestly think its worth upgrading just to play that game in full detail. Oblivion is the lastest example, ive just bought 2 7800gtx's and a £200 5.1 setup just to play that game. I dont mind doing that though as I know that its money well spent as ill get a few hundred hours play out of it.