That web site I posted before also lists proven builds and current price. You can see their Gaming builds here:
Game Builds
You can see new builds run anywhere from $600 on up. I'd look at something in the 1000 - 1600 range and see how it's specs compare to what RF wants.
Whatever you do, don't just arbitrarily grab one that "looks" nice and is "priced right". You have to do some research and make sure you know what you need and what you're getting. This holds true for the ones in the local store too.