If you aren't fussed with 3D gaming performance this one should do the job of running dual displays. Image display quality is pretty much the same across the board for photos, the more expensive cards are really about 3d gaming performance. This ones about £50 and has dual DVI output.
http://www.ebuyer.com/product/190752
This one would be a better performer with faster memory in case you fancied a bit of light gaming! About £75.
http://www.ebuyer.com/product/167966
If you wait a few more weeks ATI should be releasing their budget 5xxx series cards which will give you DX11 support, but its not important other than being slightly more futureproof.
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