You might consider waiting. Both AMD and intel are changing their sockets around again. Intel is 1155 and 1355. AMD will be releasing a new core for their bulldozer series.
I'd reccommend a phenom II quad core system, the motherboard and cpu will be a lot cheaper so it's less of an investment. Quad core AMD will give you heaps of power for video work, just not as much as an i5 or i7. (It's slightly slower than a quad core i5).
Spend your the bulk of your money on goodies like an SSD or raid system.
