A Core2Duo 2.33 with a 1,333Mhz FSB, some DDR2 800, either 2x 1Gbs or 2x 2Gbs for dual channel. One or two nVidia 8800GT cards, an nForce 650i or 680i equipped motherboard, a SATA2 HD, an X-Fi Xtreme Gamer sound card, and you should be set to go
I can provide you with US links, just too tired to grab some UK ones