UE4 computer under $600 USD in 2016

Two good alternatives:

You should not go lower on the GPU than Radeon RX470 4GB. At this level more than 8 GB (of basic) system RAM is not worth it. As for processor it is mostly a decision of good single treaded performance with Intel or multi threaded performance with AMD. My advice would be Intel if you can afford an i5, otherwise go AMD.