If you can get the fastest chip, the i7 as this will help reduce rendering times. You need at least 2 Gb of RAM if you are keeping to 32bit or more if you are using a 64bit OS. Get good fast disks this is often over looked by people and can be an unthought of limiting factor in a PC. Have at least two separate drives one for the OS and one for the media.
If you have an editing program that can take advantage of CUDA then get a good nVidia CUDA graphics card.
If you want to burn Bluray disks you will need to get a Bluray burner.
I would advise you to look at the Hardware section in this forum.