Typically, you can only install low-profile video cards into SFF computers. Something like this one:http://www.newegg.com/Product/Product.aspx?Item=N82E16814102994
You use the included low profile bracket.
With SFF systems, you often have fairly low wattage power supplies. Since that is the case, your options can be very limited. You can probably get away with the GPU I recommended as long as you don't overclock the video card.