I would personally go for the 760 at that price. For $200 that's a pretty good deal I think.
The 760 and the 270x exchange blows, they're pretty close (760 maybe edging out just a bit more in some higher res), but with NVIDIA you get their drivers (Geforce experience), and shadow play.
270x does have Mantle, but we don't really know how that will pan out yet. I guess it depends on what matters more to you, if you want to go AMD for the possible Mantle performance boost in games like BF4, Thief, and more etc., later on, then go for the 270x. If you like NVIDIA's features more, then go for the 760. They're both good cards.
Powercolors are always cheapest, because they run hot.
You can get cheaper for a 7950, closer to $200. I'd wait for a BF deal for a 7950. For a couple weeks they were going on sale for like $180 after rebates.
I'm stuck on what graphics card to get.. because although I really want the R9 280X, I don't want to drop that kind of cash. and the R9 270X 2GB just doesn't seem like it's powerful enough to last me a while. Anything that is faster than the R9 270, but not as expensive as the R9 280?