The best way to get detailed buying advice is to fill out the info requested in the
How to Ask for New Build Advice thread. Specifically, monitor resolution and any parts not needed would be very helpful.
Depending on your monitor resolution, you may be able to get something at your budget that will play on med/high settings. $550 is somewhat low end for a gaming rig, however, especially if you need to pay for a non-student discounted copy of Windows.