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I had a similar setup running for a year. The router was a Linksys WRT54G and the PCI card was Linksys WMP600N. Games like COD, Black Ops, Flight Simulator ran fine.
Since then, we upgraded the router to a Linksys E1000 (N router) and things are still fine.
My suggestion: get the Linksys WMP600N - http://www.newegg.com/Product/Product.aspx?Item=N82E16833124342
(For reference; I know that you are in NZ)