Well since on other forums I've seen people running 4870s with a 500Watt, you should be fine.
I will say though that this was my first choice, but would obviously put you R300 over budget:
Corsair TX750W Power Supply - 750w Price: R 1,776
After I added everything up though I was waay overbudget. Obviously I just chose components and then afterwards tried to get the pc down to fit budget. I see now that I missed a nice one that I recommend over that 550W.
Corsair TX650W Power Supply - 650w Price: R 1,464
So my final recommendation is to take the 650 Watt. Less than R100 overbudget.
If I enter your proposed pc into
this calculator it says you only need a 481Watt psu.
I'd still recommend the 650Watt though for breathing room.