As sincreator suggested, a 290 is also a viable choice and should prove to stay slightly under his budget while not getting too far from a 290x, no matter the partner he's buying it off to. I'm not so sure of this, but as far as I know, if going 290/290x he's better off with a Sapphire Tri-X OC rather than an ASUS. I'm owning the 290x DCUII OC, it runs great, cool enough and is dead silent unless you're manually cranking up fan speed, but those 100°c VRM temps are a huge no-no. I suppose the 290 doesn't go too far from that...
If going NVidia, anything above a 770 will exceed the budget on a range between 20$ and 100$, depending on partner and the place he's buying it from. So, should he want to get in the upper tier, he'd be restricted to AMD.
Really tho, you can usually achieve really good graphics without maxing out everything. So, getting an NVidia just because they're putting tech into the game (like almost 90% of the games out there which sport that silly "The way it's meant to be played" sticker/opening trailer) and thinking it'll run better on them because of that is not a good reason IMO...