single or dual rail psu with agp upgrading to pci-e > but then only maybe to sli?

[bods-wallop]

Hi

Im going to get a new psu and im wondering what i should actually get. Wattage and ampage are not my boggle but whether i should get one with a single 12v rail or one with 2 rails.

Furthermore, i understand that dual rails are typically for sli, but i dont really know if im going to go that route or not. At the mo i have agp on s939 mobo, but after the venice cores come out (if they overclock notably better than winchesters) ill get one and ill probably just get a pci-e board for good measure. But my problem that i see is that i dont know if i will "definately" be getting an sli board instead of just pci-e, so i dont know which i should get.

Also, even if i do get an sli enabled board, i wont go out straight away and get 2 video cards, ill start off with 1 and then upgrade to the second one further on down the line.

So basically my question is will a dual 12v rail psu work [as good as any single rail psu] in a single gpu setup? If yes, i can just get the dual rail and be set for whatever upgrade path i decide to take, whether sli or not it doesnt matter, just a bit of money wasted (compared to a lot if i go single rail but then decide on sli).

Im worried about the ampage on the dual rails in single gpu set, they're as low as 18a.

I hope you can understand me. Thanks.

[StormPC]

Yes dual +12V rails is a good thing but not necessary even for SLI. Get something like an Antec Neopower 480. They are fantastic and have every connector you could possibly need. It is one of the most stable 480 watters I've ever tested.