jaimelmiel :
No on the PSU. R9 280- 550 Watts, R9 285- 520 Watts
Maximum power consumption measured.
Typical peak power consumption.
I am just giving the Amd Recommendation. It does not hurt to have a little extra. With the power supplt you co not want to little.
The CX provides 456W on the 12v rail.
The FX 6300 uses peak power of around 130w.
So 130w + 250w = 380w...
He is perfectly fine with that PSU as long as he avoids overclocking.