i wouldn't think it would work for a 5870 xfire.
1st, the 5870xfire would require a minimum of 600w psu, you are just 20w over the minimum requirement. I might say that your power from the PSU does get distributed all around your pc for the other peripherals to work....the motherboard, the cpu, the hdd, the optical drives, fans, etc. Just having 20W above is really pushing hard on the limits.
Yes it would work, but to close for my comfort. As sid pointed out you lack enough PCIe plugs. You can use adapters, but your cutting it pretty close. I to would look for one with enough plugs and more like 750-800W.