Final piece: PSU. Will it work?

[Presnell]

I'm putting together parts for my first desktop. Just about the last bit is the power supply. I've done a fair amount of research, but still haven't come up with a completely solid idea of what I need. Here's a list of what I've got:

Already ordered:
Intel Core i5-2500
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115073

G.SKILL Ripjaws Series 8GB (2 x 4GB) DDR3 1333 RAM
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231311

EVGA Z68 LGA 1155 motherboard
http://www.newegg.com/Product/Product.aspx?Item=N82E16813188097

Looking to order soon:
Antec DF-85 Case
http://www.newegg.com/Product/Product.aspx?Item=N82E16811129087

XFX HD-687X-CNFC Radeon HD 6870 2GB video card
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150563

Corsair Force Series 3 120gb SSD
http://www.newegg.com/Product/Product.aspx?Item=N82E16820233206

Windows 7 64bit

Still searching:
Wireless adapter (probably internal and either USB or PCIe, depending on which I find is better/cheaper)

BluRay/DVD/CD read/write drive

Of note:
There are 5 120mm LED fans and 2 140mm fans on the proposed case.

I will not be overclocking this rig, I'll just be running it all as is.

I'm also trying to spec the PSU for future upgrades, including an additional 250gb+ disc hard drive, crossfire config with an identical video card, 2 more sticks of the same RAM, and a sound card.

From what I've been able to add up, all of this will pull around 800-ish watts. This is calculated after I dived into Google to find the peak wattage for all of these products from benchmarks and such. Alternately I used this wattage calculator:

http://extreme.outervision.com/PSUEngine

and came up with a somewhat similar result. I've also learned that the voltage rails in the PSU are just as important.
A couple problems. I have yet to find a clear way to determine what Amps I need my 12V rail to carry. I think it's the watts divided by 12V, so about 71Amps (850/12=71). But I'm also aware not all of the computer hardware will share the 12V rail(s) as some will be on the 5V and the 3.3V. I haven't been able to find out clearly which parts will receive power from which rail.

Originally, this Corsair AX850 power supply was in my mind:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139022

But now I'm thinking this may not be enough. With 850 watts and a 70Amp 12V rail, I think it may be cutting it a bit close, so I'll upgrade if needed, depending what I find out.

Any thoughts or good resources on the topic of PSUs and determining what a computer needs? Keep in mind, I won't be overclocking and will be using this mainly as a gaming rig, so I'll be pushing the video card a fair bit. Thanks!

 

[claptonman]

850w will be plenty for two 6870s. Even a 750w PSU will be plenty. But you are correct that amps are just as important. The unit you chose would work well, but again, a 750w version of that corsair would be fine, too. Best brands are antec, corsair, silverstone, seasonic, NZXT, PC power and cooling, and xfx.

 

[Presnell]

Thanks a lot! But when I added it all up, (2 video cards at just under 500W, i5-2500K at 130W when overclocked (I will not do this, but using as a buffer), 25W for 7 case fans, 60W for 4 sticks of RAM, 150W for motherboard, 30W for a Bluray drive, 10W for a wireless card, 10W for an SSD, 30 for a disc hard drive, and a 50-75W buffer just in case.) I get up to nearly 1000W. Doesn't seem quite right too me, but there it is. I realize I'm being rather generous with some of these figures, but I'm ok with that. If anyone thinks some of these are wildly off, too low or too high, let me know.

 

[cabinfever1977]

i dont belive those things use that many watts

 

[jonnyp11]

pretty sure all of those are really high, it doesn't say the processor or anything used, but this it would most likely be the i5-2500k, and in crossfire under load they're only pulling about 415w, leaving a good headroom, that doesn't mean a 500w will be good, as it would be under severe load constantly causing an early death, but a 650-750w should be fine.