honestly if you get the i5 it'll consume much less power, thus you can get a smaller power supply, with that money saved get a better gpu,ssd, or step up to the K version haswell so you can overclock with a z87 board. Intel is technically better, much better in single threaded stuff.
see if you can find an ivy bridge xeon cpu and you could save money with a cheapish ivy bridge mobo..that way you get hyperthreading 8 threads. Or take a look at a used 2500k.