Building a new machine in the next two weeks. Various threads on these forums talk about the great performance of each, wondering if anyone has spent time comparing the i7 5930k ($580) and the i7 5960x ($1049). I'm trying to decide if the 8 cores would provide another 30% improvement in rendering speed. My current machine is an i7-2660k from May, 2011 with 16 gigs of ram and a couple of newer SSD's.
This video (at 11:26) shows rendering with Vegas and the two chips at stock and overclock.

If my math is right, looks like a 16-18% performance boost going from 6 to 8 on this specific example.
Any other thoughts between the 6 core and 8 core? I keep my machines for 2-3 years and use it for audio and video editing.
Thanks for guidance.
Sean
Broadcast Voice Over Talent
http://www.seancaldwell.com