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Sorry to come in at an angle here but is that Radeon 6850 significantly faster than my Radeon 4890 1GB?
Asus HD 6850 DirectCU V2 1024MB GDDR5 PCI-Express Graphics Card £99.95 inc VAT
http://www.overclockers.co.uk/showproduct.php?prodid=GX-269-AS&groupid=701&catid=56&subcat=1866
Great performance for £100
Definitely the 6850. It's an excellent sub £100 graphics card.