You fail to mention screen resolution which makes a massive difference. At 1080p I'd say about 34 FPS average. The HD 7850 is not exactly the best GPU, but it can be overclocked towards 1GHz, which makes a notable difference. Unless you are willing to put money into a better GPU, I suggest you do not play on 'ultra'.
Avaruz is pretty much spot on. Start at Ultra, turn a couple of settings down a little, and you'll be absolutely fine at 1080P. If you want to guarantee solid fps even when things get really busy, you might need to drop a few more settings. It's still a great card.
Here's a very similar build I already had saved, obviously it has a nicer motherboard and cooler for overclocking and bigger HDD, but it's definitely in the same area as your build which is presumably going to cost $550-600 when you allow for PSU and case. PCPartPicker part list / Price breakdown by merchant / Benchmarks