It's not terrible. I would not purchase any card above a R9 280X to pair with it. A 270X or 280 would be great, though.
If you're willing to spend an extra $30 bucks, get an FX-8320. Twice the amount of cores. Alternatively, the FX-6300, is usually within $10 of the FX-4300 in cost, so that would be the best bang for the buck.