Thanks for the reply, but I was looking for more of a direct comparison - i.e. will it make any significant improvement ? If I can't get at least 30% more power (in terns of frame rates etc on recent games) it isn't worth doing.
If anyone is still interested I can report that I opted for the HD3850 as suggested by wjrt and citadel. This upgrade was well and truly worthwhile, and doubled my 3DMark score with a single component upgrade. The games mentioned all run smooth as silk.
12 months later the card is still going strong (although I changed to a quieter cooler) and I am still very happy with it.
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