I'm not noticing any difference in editing (different than rendering) on the 4.4ghz 8320 vs 4ghz 4930K. It is rendering where there may be any difference. These CPUs are both essentially quads with hyperthreading. Intel is about 65% more efficient on single thread, but AMD has more efficient scaling on multithread (about 5 vs 6). That means that in equal clocks, the intel should be around 40% faster. A 3.4GHz Xeon should then be around 4.76GHz FX.
After doing the math however, you are most likely correct about not surpassing the Xeon, but it should get within 5% - 10%. If you take the $60 savings and put it to a GPU, then the AMD system will be stronger than the Xeon. If I had the knowledge I have now, I would have opted for the AMD build over the 4930K, because honestly, I have not rendered anything where I would save more than an hour on the 4930K over the AMD and as I said, I am noticing no difference in the actual editing process.
I think AMD has a bad reputation because they do not have super high end CPUs. I think the build you recommended is an excellent option (I would not even recommend anything higher priced until a 5820K is within budget) and the OP cannot go wrong either way. I feel that getting the $60 savings and putting toward a better GPU would be a better choice. AMD gives just a tad more in options on a budget.