E8400 is below an i3 at stock and probably on par with a G2120. ANY i5 on the market would DOUBLE the performance you currently have.
No one cares about NICs because aside from Intel's superior prowess in that department, everyone is just "good enough" for most but not on par with Intel's NICs.
If you actually need an LGA 2011 board or chip, and you might since BF4 loves more cores, you might as well get a i7-3820 now to tread water first and then upgrade later to Ivy-E. The few months with the i7 will please you compared to the E8400 you have now.