a server for cpu intensive encoding might be over your budget, the best shot would be Quad Core Dual Xeon.
Within your budget we can offer you i-7 or Xeon, say our standard offer is:
Intel Core i7-920 2.66GHz
3GB KIT DDR3
There are lots of other deals available at http://www.natcoweb.com/build_your_server.html
Please pm if interested.