Core 2 Duo was fast, Core 2 Quad was stupid fast, and Core i5/i7 is stupidly fasterer.
Quicktime has some pathetic encoding speeds though.
http://www.cpubenchmark.net/cpu_list.php
i come across not sure anyone else already posted or not.
Core 2 Duo 3.06Ghz ranked 124
Core 2 Duo 3.30Ghz ranked 104
Core i5 750 2.66Ghz ranked 39
Core i5 860 2.80Ghz ranked 12