Hi i'm currently working on building a new computer and i came to where i needed to pick out a power supply. I read up in several places about 12v single rail or multiple rail, and it seems the general consensus is that their isnt really a difference. neither one will give you much of an advantage and as long as theyre well built by good manufacturers, theyll each be able to do the same thing.
but then i talked to my friend, who insisted that with a single rail psu, i wouldn't be able to run 2 graphics card (sli or crossfire) or have multiple hard drives. that i needed a multiple rail psu to split the power for that, i tried correcting him that it didn't make a difference but he was sure it did.
the computer im building initialy would be fine with any of these threes, but i kind of want it to be the last computer i build so it being able to last through stronger video cards (including sli or crossfire) and multiple hard drives is ideal. also i'm just noticing the 850w one isnt core i7 compatable, how is that possible?
The 620w is actually a single rail unit, there is no overcurrent protection on any of the 3 virtual rails. http://www.hardwaresecrets.com/article/371
Any of the 3 power supplies you listed would work fine, if you're looking to SLI or Xfire higher end cards the 850 would be the way to go.
Do you get email from Newegg?
They currently have a promotion that takes 20% off the cost of the Corsair 850 making it about $100 after rebate, that's a hard deal to beat.