At stock, the CX430 is mostly certainly enough, even with Bulldozer's poor power consumption control. Only thing is, you need a molex to 6 pin adapter to make it work with a 7870
Total system power consumption was 226 watts with the FX-4100 and a 6950(6xxx means older, which means more power hungry. x9xx means higher level), and this is "at the wall". After multiplying "at the wall" readings by the efficiency percentage, that nets you what is actually delivered to the motherboard/CPU, and that value is what determines how close to the PSU's max wattage you are.
Using the 226 watt value in the review, you multiply it with 87% (HX850 is 80 Plus Gold certified, so it is safe to assume that percentage), and you get 196 watts of power consumed by the components.