Technically any video card would be compatible as all graphics cards use a pci-e port. I would recommend some form of Geforce 560ti, On ebay you can pick one up for around £60/ $100 or if you hold out maybe a 570 (That does need a 550 PSU). Soon you may be able to get a 650 up to the 660 they are more easy on the psu and don't require such beastly psus) (DO NOT GET A GT CARD FOR GAMING OR GRAPHICS DESIGN) Or from an Amd stand port maybe an R7 250/250x/260. Or the older 7750/7770/7790. For the implied budget. What is the actual budget and what will your usage be? And do you know what PSU it is? (As that will be a limiting factor of your PC). Please post model number and full specs. Also some dimensions of free space in the case and how...