optiplex 1030 mt

Hello all, i have a Optiplex 3010 MT with I-5 3470 after market case, ssd, 600w PSU and 8g of ddr3 ram i really trying to get a GPU that would work the best for the $200 mark, i seen some nvidia ones and some amd which i have no clue about the amd side of things, some are 4g and some are 8g of...