I dont know why the prices are so cheap right now.... maybe because r520 and geforce7 have been anounced... but anyways, you can pick up some really good video cards on ebay for super cheap
radeon 9700- $60
radeon 9800- $80
geforce 5900 - $80
these were cards selling for $200 not a month ago... a radeon 9700 will play any game out today (doom3, hl2) in high quality, easily.