Benchmark Results: Audio/Video
Any performance benefit you see in iTunes or Lame is attributable to a top Turbo Boost setting that's 100 MHz faster than the Core i7-2600K. Architecturally, the two CPUs should otherwise behave similarly in a single-threaded benchmark that only taxes one core.
Video encoding or transcoding is typically a perfect application for multi-core processors, as most apps written for this discipline are able to exploit all of a processor's available resources. Therefore, Sandy Bridge-E's decisive win in each test doesn't come as a surprise, but is impressive nonetheless.