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Don't bring AMD cards recommendation into this (yet)...some people won't be happy.Agreed, a 290 would be a much better option than a 960.
http://www.overclockers.co.uk/showproduct.php?prodid=GX-166-PC
If you've got £200 don't waste your £££ on a crappy 960, get a 290, it blows that card away. The problems with AMD cards and WOW are totally overblown (as usual).
Best Nvidia card for WoW
I've just done a quick Google on your stuttering problem, and it seems that the stutter may be due to the WoD expansion pack and nothing to do with the GPU. See this thread here.