I'm looking to upgrade my current set up of three iMacs to something that can render faster and with more cores...I use Blender an open source piece of 3D software... The confusion comes here, I have two fairly recent iMacs one a 3.4 Ghz i7 with 16 GB 1600 DDR3 ram ( this is early 2013 ) the other a 2.8 Ghz with 12 GB of 1067 DDR3 ram...in rendering 3D scenes, with both computers using 8 threads the 3.4 is almost exactly 2x as fast as the 2.8. So what in the specs account or is responsible for this? It can't be Ghz or Ram alone... As a side note the 2.8 runs like an oven, the 3.4 is barely warm when at full pelt. So in upgrading to pro's apart from more cores what is going to create a rendering speed boost?