So I'm probably getting the 280X but I don't know if I'll need to upgrade my power supply, I'm currently using a Corsair CX600. I'm guessing I probably will but I can't seem to find anything about it. Any help would be great.
thats good enough for an R9-280x. you wont need more than 600w for a single GPU Build.
You should be fine. You might reach 600 watts if you stress both your 8350 and 280x to the max, but it shouldn't be a problem.
That's easily enough. You could run it on 500 or less, providing you don't stress it with some synthetic benches. You will never use that amount of power while gaming.