This rendering benchmark based off of the Cinema 4D engine is a terrific indicator for multi-threaded processing.
POV-Ray 3.7 Beta
POV-Ray has long been the poster child for multi-threaded processing and rendering.
Blender is a free open source 3D engine that is a popular choice amongst college students and small developers.
The performance of the Core i7-3820 and i7-2600K are again matching up pretty evenly.