Comment on this PC build please. :)

[StarSolitude]

Note: I know these topics are all over the place and are annoying, but I ask here because I have nobody in real life I can discuss this with, or even on MSN.

I've been inspecting components for a new PC for a while now. This is what I've come up with so far...
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Budget: £800-900.
PC Usage: High-End Gaming / Power User

Motherboard: Gigabyte GA-EX58-UD3R Intel X58 (Socket 1366)
Link: http://www.overclockers.co.uk/showproduct.php?prodid=MB-159-GI&groupid=701&catid=5&subcat=1283
Price: £135.99

CPU: Intel Core i7 920 2.66GHz @ 4GHz
Link: http://www.overclockers.co.uk/showproduct.php?prodid=CP-280-IN
Price: £211.99

CPU Cooler: Corsair H50 Watercooler
Link: http://www.overclockers.co.uk/showproduct.php?prodid=WC-001-CS
Price: £59.98

RAM: OCZ Gold 6GB (3x2GB) DDR3 Tri-Channel
Link: http://www.overclockers.co.uk/showproduct.php?prodid=MY-151-OC
Price: £82.00

Graphics: XFX ATI Radeon HD 4870 1024MB GDDR5
Link: http://www.overclockers.co.uk/showproduct.php?prodid=GX-120-XF&groupid=701&catid=56&subcat=939
Price: £99.98

Hard-Drive x2 (Raid-0): Seagate Barracuda 7200.12 500GB SATA-II 16MB
Link: http://www.overclockers.co.uk/showproduct.php?prodid=HD-206-SE&groupid=701&catid=14&subcat=940
Price: £73.96 (36.98 each)

Case: Antec 902
Link: http://www.overclockers.co.uk/showproduct.php?prodid=CA-110-AN&groupid=701&catid=7&subcat=160
Price: £87.99

Power Supply: Corsair TX 650W ATX
Link: http://www.overclockers.co.uk/showproduct.php?prodid=CA-008-CS
Price: £77.99

Total: £829.98
Left to spend: £100 MAX.
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I am unsure about the graphics card. I play games @ 1400 x 900. It may be wise to spend an extra £100 on a graphics card, just to future-proof the system some more, perhaps an ATI HD 5800 series card?

Anything you think I need to change or consider with this potential build?