Acer Aspire 5536G
744G32Mn, AMD Turion RM-72 Dual Core Processor, 15.6" HD Screen, Windows Vista Home Premium Edition, 4GB RAM, 320GB HDD, DVD Rewriter, 512MB Dedicated Graphics, Webcam, LX.PAZ0X.092, was 579.79
The ATI 4570 graphics card is very capable for games, and should according to notebookcheck.net (http://www.notebookcheck.net/AMD-ATI-Mobility-Radeon-HD-4570.13885.0.html) be able to handle Left 4 Dead at around 48fps in high detail. So should be roughly twice as fast as an ION netbook.
In fact I think this is the notebook with the fastest graphics card I've seen for less than £400.
Oh, also qualifies for the Acer's Windows 7 upgrade if you order soon (upgrade offer expires 31st Jan)