Regarding the claims about whether the PSU is enough, although the RAM sticks were found to be faulty, may I point out that its the railings of the PSU which are much more important that the actually wattage number quoted. I don't know the exact technical details, I'm sure a google search would suffice, but when I was looking for a PSU a while back, that was the common consensus, check the railings, not just the quoted wattage.
Multiple rails really just means one thing: individual current limiters for individual lines instead of a collective current limiter for all lines together. In both cases you most likely just have a single current source so it isn't as if a multiple rail PSU can sustain more power draw per line or overall more power draw than a single rail PSU.
For example, say you have 12 Volt current source that fans out into 3 lines that ultimately fan out into N power connectors. If you have all 3 lines controlled by a single limiter circuit then you have a single rail. If each line has its own limiter circuit than you have three rails. In practice, the only difference is how the limiter works. You still have to provide the required amperage per line without burning out as per the spec. You could over-shoot or under-shoot the amount of amperage you are suppose to provide per line in either case (thicken up or thin the traces).
It'd be a different story if you were really getting a power supply with individual current sources per rail (I'm not sure if they make those but I would imagine so at very high wattage rated PSUs, though they may just thicken the traces). One reason you might want multiple rails is in the case of a defective power supply - it could damage less equipment if there are individual safety shutoffs per line. Basically, it might only fry the equipment on only a single line if shorted instead of all lines.