How about buying 2nd hand 4870 for around 40-50? Will give you a decent boost over 8800gtx and tide you over until full upgrade.
Remember that there should be 69xx series and 560/570 out by January so if ur going to use ur gpu to its full potential now, later the prices will be cheaper and there might be a lot better options as well.
Remember that there should be 69xx series and 560/570 out by January so if ur going to use ur gpu to its full potential now, later the prices will be cheaper and there might be a lot better options as well.