I just made this: http://pcpartpicker.com/p/YY3V8d
It's got a CrossFire compatible mobo, so you can add another 290X in the future (you'll need a bigger PSU though) if the horsepower isn't enough.
I have personal experience with the i5 and it's a great processor that you can get at a microcener for $160. You only need 8 GB of memory for now, so don't go for 16 unless you either want to carelessly spend money or you need it for a specific task. Both storage solutions are good (though I don't have personal experience with SanDisk, anyone else?) and you'll love to have an SSD for booting and commonly used programs. The 290X is a BEAST and will last you a long time (I even made room for a second 290X to be implemented with just a different PSU). The case is easy for first-timers, and cheap, so good to go. The PSU is something a lot of people have (including me, sadly) cheaped out on, but it is NOT what you want to cheap out on at all. A bad PSU could destroy your entire system, so SeaSonic or Corsair's AX, RM, and HX series' are the way to go. DO NOT SKIMP ON THE PSU, PLEASE. For under $800, this is a darn good PC, you just need a monitor, OS, and Mouse which can be found for cheap. (I didn't see you mention that you need these, so I left it out, can change this if necessary).
If anyone has personal experience with the parts I don't or alternative views, chime in. More thoughts are great.