We know the regular FX-8320 is qualified, and it's the same price as the 'E' (as of now).
The -E is simply a newer chip (and likely higher-binned). Though the base speed is a bit lower the Turbo speeds are the same.
I suggested the -E because it's flying past the older model FX-8320 in OC'ing, is 95w, and would be a near-perfect solution for a 4+1 phase motherboard like the Gigabyte.
What CPU are you using, now?