Would my CX600 be enough?

Solution
A Radeon R9-290X needs 33 amps on the 12v + rail and a 600 watt power supply with 1 - 6 pin and 1 - 8 pin PCIE power connections.

The CX600 IS SUFFICIENT to power your specs with a 290X.


You are right that the seasonic 550w is better quality, but quite frankly, it is very stupid to go out and buy another psu (especially one with lower wattage) just because it is slightly better designed.

@mortarmelon
The CX600W will work fine.
 


550W is still enough for a FX 8350 and R9 290X, it's just less headroom. 650W is just insurance.