Ok here is a start. This will be a very good gaming spec. I have allowed for a second 580 to be added when need be. This spec includes everything you should need, please tell me what you think!
Here it is:
Case
COOLERMASTER HAF 912 PLUS MID TOWER GAMING CASE
Processor (CPU)
Intel® Core™i7-2600 Quad Core (3.40GHz, 8MB Cache) + HD Graphics
Motherboard
ASUS® P8Z68-V/GEN3: PCI-E 3.0 READY, SLI, CROSSFIREX
Memory (RAM)
8GB KINGSTON HYPER-X GENESIS DUAL-DDR3 1600MHz, X.M.P (2 x 4GB KIT)
Graphics Card
3GB NVIDIA GEFORCE GTX 580 - 2 DVI, HDMI, DP - 3D Vision Ready
Memory - 1st Hard Disk
1TB WD CAVIAR BLACK WD1002FAEX, SATA 6 Gb/s, 64MB CACHE (7200rpm)
1st DVD/BLU-RAY Drive
24x DUAL LAYER DVD WRITER ±R/±RW/RAM
Memory Card Reader
INTERNAL 52 IN 1 CARD READER (XD, MS, CF, SD, etc) + 1 x USB 2.0 PORT
Power Supply
CORSAIR 850W ENTHUSIAST SERIES™ TX850 V2-80 PLUS® BRONZE (£99)
Processor Cooling
SUPER QUIET 22dBA TRIPLE COPPER HEATPIPE INTEL CPU COOLER (£19)
Sound Card
ONBOARD 6 CHANNEL (5.1) HIGH DEF AUDIO (AS STANDARD)
Network Facilities
10/100/1000 GIGABIT LAN PORT - AS STANDARD ON ALL PCs
USB Options
6 x USB 2.0 PORTS @ BACK PANEL (MIN 2 FRONT PORTS) AS STANDARD
Operating System
Genuine Windows 7 Home Premium 64 Bit - inc DVD & Licence (£79)
Office Software
NO OFFICE SOFTWARE
Anti-Virus
NO ANTI-VIRUS SOFTWARE
Monitor
IIYAMA E2473HDS 24" LED WIDESCREEN, 2 HDMI/DVI-D 1920x1080 (£159)
Keyboard & Mouse
LOGITECH® MK250 WIRELESS KEYBOARD & MOUSE COMBO (£21)
Warranty
3 Year Silver Warranty (1 Year Collect & Return, 1 Year Parts, 3 Year Labour) (£5)
Delivery
STANDARD INSURED DELIVERY TO UK MAINLAND (MON-FRI)
Build Time
Standard Build - Approximately 8 to 10 working days
Quantity
1
Good spec suggested by Music Guy. You could drop the PSU down if you don't see yourself adding another one in to save some money. The 580 Should last you a few years before it will start to struggle