i would get a gtx 770, which you can get for about 310 bucks, and an amd 8350 for 190 bucks. Those will allow him to play on ultra settings. As a PSU i would recommend a 600w 80plus bronze (since you are on a budget) such as the corsair cx 600. Add in a wd blue hard drive and the cheapest 8 gigs of ram you can find (in my area its kingston hyperx for about 70 bucks), put in on an am3+ board of your choice and you got a high-ultra rig for well under a grand. Of course you can use an ssd, more efficient psu, or an intel cpu if you want to spend the entire budget. However this won't push gaming performance much.