Power Supply needed for OCed Xfire system

With the system I'm currently building I intend to do some overclocking of the CPU and RAM as well as eventually get a second video card for crossfire. As it stands I'll be getting a Phenom II X4 955, 2x2GB of G.Skill DDR3 1600 RAM, and an HD4870 video card. Eventually I'll be getting a second video card to pair with the one I have.

So I'm wondering what kind of power supply would be required to run all of this. I've been looking at the Corsair 550W and 650W PSUs (both have a single 12V rail - 41A and 52A respectively), the OCZ ModXStream 600W and 700W PSUs (both of which have two 25A 12V rails) and the Antec Earthwatts 650W PSU (Which has 3 12V Rails at 22A, 22A and 25A).

I'm leaning towards the earthwatts one right now, as it is significantly less expensive than the corsair and I'm afraid the 25A rails on the OCZ ones might not be quite enough to power both a video card and the OCed CPU at peak (since I'd have to put the CPU on a rail with one of the video cards).

So, is 650W going to be enough for what I want? A friend of mine who had a similar setup told me that her Corsair 650W wasn't able to handle everything and ended up dying. I'm not sure if it was a bad PSU or if it really wasn't enough.

Also, is the Antec Earthwatts a good name? Will the 3 rails work well for what I need? Or would I be better off spending the extra $20 on the Corsair with the single rail?