I think the 370z should be out of the running since we are a little biased and its pretty much a given.
For around $70k or less and judging purely on cosmetic.....
1. Jaguar XJ
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2. Porsche Cayman R
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3. Alfa Romeo 4c (Not currently in production just yet though)
Runner up's
-Audi TT RS
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-Mustang Boss 302
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-BMW M3