Either a GTX 780 or a R9 290. And for the sake of simplicity, they both have stock coolers.
My friend said he'd rather go with an R9 290. I think he's wrong.
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While Wargamer has posted a link summarising why to buy the 780 over the R9 290X, here are a few reasons for those of you who don't want to leave the site: GTX costs more but runs far quieter and at much, much lower temperatures. 290X is essentially running flat out when outputting high detail and res, while the 780 seems to be jogging, with much more energy to spare. A nice analogy from Tech of Tomorrow, I feel. The 780 costs more but you get a much nicer-looking and better-built card for the money.