Sounds like an excellent on-board graphics system. My suggestion would be to continue to use the on-board until you come across a game you have trouble with. At that point purchase a low cost upgrade with high reviews. I will attach a link to newegg.com below with compatible cards.

The thing about graphics cards is the prices drop like rocks, so the longer you can hold out and get away with using your on-board, the more bang you will get for your buck when you decide to purchase a graphics card.

The following cards will work with your system, simply click on the price range on the left to see exactly what you can afford. Also, as a side note, these are sorted by best "rating" rather than lowest price. You may want to resort while you are looking for something you like:

http://www.newegg.com/Product/…..ageSize=20