Take your pick, priced low to high. In order of performance R9 290>R9 280x>GTX 960
http://uk.pcpartpicker.com/parts/compare/gigabyte-video-card-gvn960ixoc2gd%2Cgigabyte-video-card-gvr929wf34gd%2Cxfx-video-card-r9280xtdfd/
Make sure your PSU is adequate for the graphics card you choose.