r9 270 for amd (The strongest one for that $200 limit i believe). nVidia would be the 750Ti or the 660 or something along that area for under 200$. The AMD would be a stronger choice in my opinion.
ATI Radeon R9 270x :http://www.newegg.com/Product/Product.aspx?Item=N82E16814129281&nm_mc=AFC-C8Junction&cm_mmc=AFC-C8Junction-_-na-_-na-_-na&cm_sp=&AID=10446076&PID=3938566&SID=