If you read the thread that Ajay mentioned and still have questions or want to fine-tune your specs, please let us know
In short, Windows 7 64bit (you need 64bit to use more then 3GB internal memory)
Cores, starting from 4 i suggest.
Display, its a screen, we work with simple 23inch samsung screens, nothing special.
We got our new computers this week. So we took 64bit win7 with 8gb memory, Nvidia Quadro 600 graphics card and Intel Xeon CPU31235 3.20GHz (8 cores) prosessor. Hopefully things runs smoothier from now on.