1) Seasonic s12ii 520w bronze plus 2) fsp aurum gold 500 w
Which one is better to get? They both cost exactly the same in my country.
MSI z77-g45 i5-3570k (will be OCing to 4.5) hd 7850 (will be ocing to max) wd caviar black 1 tg 8 gb corsair vengeance ram
More aboutchoosing psus
Cooler Master Silent Pro 600W or 800W. Never worry about PSU again.
I'd say get the FSP. It's more efficient, so it'll put out roughly the same wattage as the Seasonic. The only thing that I'm not so sure about is the amperage: the Aurum puts out 18A on two 12V rails, whereas the S12II puts out 40A on one 12V rail. I don't know how much of a difference that'd make, but truthfully you can't go wrong with either of these PSUs.
So it's as easy as that - just the sum of all rails' amperages? Is there any way that dual rail PSUs are different than single rail PSUs in performance/reliabilty/stability?
I would vote for the Seasonic. It is a known high quality unit. It will deliver 40 amps vs. 36 for the fsp.
Nomally, you can't just add the amps from multiple rails, but in this case, you can. What you do is look at the data plate which will give you the combined amps, or watts which you can divide by 12. FSP is a good unit though, you would do well with either.
Dual rails is a safety feature which limits the amps that can be delivered. It really makes no diffrence at all.