Check this. Think about that, for encoding, it will save u ton of time. Mobo will not make any impact that u can see in the real life.
I would have rather low end mobo in the premium 2011 class, than nice mobo, but weaker CPU. I know it cost more, (about $200 difference in your case), but its more practical.
Get water cooling and OC to 4.6MHz or so and have an high end machine.http://www.anandtech.com/bench/Product/443?vs=552
Intel Core i7 3820 - 3.6GHz - 1MB L2 - 10MB L3
Intel Core i7 3930K - 3.2GHz - 1.5MB L2 - 12MB L3
$299.99 vs $589.99
ASRock X79 Extreme3 LGA 2011 Intel X79 SATA 6Gb/s USB 3.0 ATX Intel Motherboard
was: $219.99 -> $209.99http://www.newegg.com/Product/Product.aspx?Item=N82E16813157287