I need help buying a new PSU?

Hi everyone!

I recently built myself a nice new quad core AMD desktop and I also have 2 nVidia 9600gso graphics cards utilisting SLI. The problem is that I was using a cheapo 650W PSU which blew on me.

I dont mind too much as I paid £40 for this PSU 2 years ago. I kept it from my old PC and to be honest, it didnt really do such a great job anyway.

Anyway, basically, I need a new one now. The new PSU has got to have 4+4 for the mobo (which the old one didnt have) aswell as 2x6pin for sli. The thing is though, I dont understand rails, etc.

On nVidias website, its says that my card needs 105w to power it. So multiply that by 2 is 210w. I think my CPU is around 100w. I have no idea how much the mobo takes or needs. Also no idea how much the ram and hdd needs.

Apparently, its not about watts though, its about quality and also ampage. I know quality but i have no idea about ampage.

How many amps do i need? Do i get single rail? dual? Do i need ampage on both rails or just one? How many watts will i need? I have no idea how it works.

The mobo manual says to get a 1000w PSU but thats rediculous and I know people who have SLI running perfectly with nowhere near that kind of power.

Please could someone explain how it works?

Thanks, Ant...