One can run this game with pretty crappy hardware but the beauty is when you can max most or everything. Anything less would be like banging Britney Spears wearing a blindfold (you, not her). ;-)

Not less than 560 for 1600+ resolutions imho. And for this price range I would recommend to go for an ATI.

It could be more cost effective though to buy a 2nd hand CRT monitor and play in 1024 resolution :)