An R9-280 is roughly equivalent to a GTX 960 in actual performance - but it's made by AMD, costs less, and uses more power.
I think it would be a better choice because you could later add R9-280 card(s) to run in a CrossFire configuration. If this is your plan, then I advise paying a little more upfront to save yourself a lot more down the line by buying a robust PSU which can handle multiple GPUs.
An AMD GPU also allows the "R7" iGPU in your AMD APU to assist a little in graphic computations instead of just sitting inert. Admittedly, this is a weak contribution and it would bump up the heat output of your processor package, but AMD designed it to work that way anyhow. And not all software (now or upcoming) can support this fancy little AMD technology, so you might want to determine if it applies to any particular games/applications you want to run.
Personally, I would advise an AMD FX-83xx/93xx CPU running on an AM3+/990FX/SB950/DDR3 motherboard. It would cost about the same but give you a wider selection of motherboards to choose from, which offer more compatibility options with existing and upcoming technologies, and more power-user or overclocking toys to play with. The AMD APU parts are designed more for "all in one" sorts of PCs intended for browser and productivity sort of things, basically non-gaming (or perhaps light-gaming) systems which don't require added GPU hardware. Why pay extra to put a junky (and largely unused) GPU into your processor when you can instead buy a plain CPU for less and use that money towards upgraded GPU card(s)?
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