In that range, you're looking at either an AMD 7770 or an Nvidia 650.
The 7770 will have the edge in terms of raw speed. The 650 will have the edge in being slightly smaller and a tad power efficient as well as running a little cooler. If you have a preference between AMD and Nvidia in terms of their drivers then that could sway your decision. Personally, I prefer Nvidia but I don't think you can go wrong with either card. The 7770 is a really good value IMO.
EVGA 650 ($99.99 after rebate) - http://www.newegg.com/Product/Product.aspx?Item=N82E16814130828
MSI 7770 ($99.99 after rebate) - http://www.newegg.com/Product/Product.aspx?Item=N82E16814127687
Both cards could run SimCity.
Here's a link comparing card performance between the two: http://www.anandtech.com/bench/Product/681?vs=536 --- Corsair 500R | Intel 3570K | EVGA FTW GTX 670 | 8gb Corsair Vengeance | 120gb Kingston SSD | 1tb WD Caviar Black HDD | Corsair 650W