From the sounds of it, your not much into gaming?
If not, Being as video encoding appears to be something you do alot of, youll want to focus on CPU power and RAM.
Without knowing much on budget:
I would go for the i7 2600K. This way, overclocking is an option in the future should you decide to try it. Its not that much more expensive than the locked version.
Find you a good P67 Motherboard that offers a good layout, and support for the periphials you want. ASUS and Gigabyte are a good place to start.
And I would go ahead and go with 8GB of DDR3 1600 RAM.
Something like these: Newegg.com - CORSAIR Vengeance 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model CMZ8GX3M2A1600C9B
Also, being as youll probably be working the CPU hard for long hours encoding, I would invest in a decent aftermarket cooler. It doesnt have to be top of the line, or water cooling. But a nice cooler that will do better than stock.
Something like: http://www.newegg.com/Product/Produc...ermaster%20212
For a power supply, if you are not pushing a large Graphics Card, you really will not need that much power. A good Quality 500-550W would be more than enough.
However, I would look into a Corsair, Antec or Seasonic (650W)
This way, you have plenty of power and theres even enough to push a higher end GPU, (like a 570) if you choose to add one later.