That appears to be a slim line chassis system. You are going to be limited by both space and power supply size. The PSU is probably a 220W slimline, and that is about the max you can put in there.
Is this upgrade for gaming?
If so, what resolution is your monitor?
Do you have a graphic card installed, or are you using integrated graphics?
The best you can do for improving gaming is to install something like one of these AMD HD 6670s.http://www.newegg.com/Product/Product.aspx?Item=N82E16814131469http://www.newegg.com/Product/Product.aspx?Item=N82E16814102958http://www.newegg.com/Product/Product.aspx?Item=N82E16814161397
But measure the length inside the case where the card will go to be sure it won't hit anything due to its length.