This is one of the 'sweet points' of the price vs speed equation: you can get faster cards, but you can pay twice as much for a 50% increase in speed or you can spend half as much and get a card that's only a third of the speed. If you have a SLI motherboard, two of these will outperform a single card costing more.
Anyone interested? www.cex.co.uk will give me £83 to spend on other things for it (and then sell it for £125!)
Update: sold to CeX.