You're not going to believe this, but the StoneRock 500 ran my 4870x2 and a E7400 (not mine, the service center's) perfectly through an hour of gaming, in an open testbed.
I was not willing to believe it myself, but it did... I don't know whether the supply was straining or not, no voltage readings, but I think that combo is about 350 watts load, which is roughly what your load will be like as well, 150 for the CPU, the same for the card an a little more for drives and fans.
It should be OK, a little dicey but just about fine.