I haven't built a PC in about 6 or 7 years. Anyone mind looking over my build before I buy it to see that everything's compatible and I didn't screw anything up? It's mainly a system to play simple games like the Lego series (Pirates, Star Wars III, etc) and do some light audio editing.
I also agree that you might want a 6670 and one of the PSU's that zooted suggested.
You don't need to upgrade your case unless you need special features on the front of it (like USB 3.0, eSata, and so on) or you are buying an odd sized mobo (which you aren't). I'm using a ~20 year old case for an Intel Atom server I built a few months ago.