Well, a friend of mine wants to build a PC at the same price so I've some ideas about your rig. To begin with, try to find a cheap case with good airflow so as to let the components get fresh air. As for the motherboard since you are not going to overclock you ought to take a cheap one with a H61(no usb 3.0 and sata) or H67 chipset. Be sure that there is a 16x pci slot for a gpu. Next, you should take at least 4Gigs of RAM. Next I suggest that you take an i5 2500. Why should you pay about 200$ for a cpu? Because it has intel hd graphics 3000, that is, that you can play some games withought the need of a separate gpu and you also get a cpu that is powerfull, durable and you is not going to have any botlenecks with it if you are to take a 6850 later. As for the PSU take one that is more than 550w and has a 25a 12v rail. This rig can save you some money if you use the hd graphics for a while. If you want to have instant power in games, you can take the 6850 imidietly. As for the cpu that you want to take, which is way much cheaper than the i5, you may have a bottleneck with it cause it only has 2 cores.