The 5850 is still a nice deal at $150. It is however overkill for your current resolution. Fortunately that Sapphire card has a lil brother in the HD5830 which is also crazy cheap on newegg and this time it is in stock;http://www.newegg.com/Product/Product.aspx?Item=N82E16814102878
Still a bit of overkill to be honest but nothing else makes sense with it selling at that price. For example it's cheaper than the cheapest HD5750 you mentioned and at your resolution it is approximately 35% faster.