I own the Dell 518, which initially came with a built-in Intel graphics "card", and any dedicated graphics card is an improvement. So 2 years ago I purchased a cheap GeForce 8400, which was an improvement.
Bought this product because the GeForce 8400 was having challenges displaying Diablo III. This card blows the 8400 away! Incredible card for the money. It rivals cards twice the price!
Display is full HD 1920x1080p in all applications and games (Diablo III included).
Just make sure your power supply is upgraded or capable of handling the 500W requirement. Most Dells have smaller power supplies. If you have to upgrade power supplies, it is worth it!