Could someone give me a seal of approval please! :o)

[flay]

Hey guys, pretty much ready to get this build up and running, I just need to select a PSU. I've tried to do some research on it, but frankly I'm still a little confused.
Specs:
cpu: Phenom II 940 - oc'd 3.4
mobo: asus M3A79-T Deluxe
ram: ocz Platinum 800mhz 4gb
gpu: 2 x HD4870's in xfire.
hdd's: 2 x caviar black 640gb's
hsf: OCZ vendetta II
optical: two very average dvd drives.
Case: Antec 900

So, because of the crossfire, I figured I should have a quite high wattage psu, but I know I need certain amps on a certain rail or some such, and thats where I got confused. an online psu calculator told me this system would draw around 558W or some such, but I think thats in ideal circumstances. Thus I figured about 750W would be about right, and leave me room for the future.

so two questions:
1) is 750w about right, or too high/low
2) these all look quite serviceable, but I need them to fit and reach in an Antec 900 case (thus would being modular help?), so could you guys please wade in with your opinions as to which ones are best?
cheers.

Some I have looked at:
Corsair
http://www.overclockers.co.uk/showproduct.php?prodid=CA-011-CS&tool=3

OCZ:
http://www.overclockers.co.uk/showproduct.php?prodid=CA-027-OC

PC P&C
http://www.overclockers.co.uk/showproduct.php?prodid=CA-004-PP&groupid=701&catid=123&subcat=1104

 

[dragonsprayer]

its really important you use a strait throuh 80mm fan and not a blow down or up 120-140mm fan

zeus 850
antec 850 or 1000

you can go too big but with 400w of gpu you want a minimum of 850 and even a 1000 is not too big

60% is the most effecient spot of most psu's - your around 600w with a raid

750 is ok

if the price of a silverstone zeus 850 is good it is what i use in smilar systems like yours!

you can see that is blow through silvestone

 

[dragonsprayer]

these go on sale for $150 with the 900 case - look for the combo deals! blow through
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371009&Tpk=antec%20850

 

[flay]

sorry, I cant look at newegg, wrong country!

I thought it was more to do with the amps on a rail, rather than the actual wattages? Do I really need 850w+? that starts getting seriously expensive and I was hoping not to spend too much over £100, like the 3 examples I showed in my first post.

Anyone else got any ideas, please?

 

[pr2thej]

On a side note, the OCZ Platinum RAM needs to have its timings and voltage set manually to achieve the advertised amount.
Overclockers are the only UK stockists of PC P&C that i know of and therefore its a little more expensive. Im a fan of big fat single rails though so that'd be my pick.
The wattage is derived from the rails ampage so its very much about both, however some more shady companies would use a high wattage to make their product look better, with weak rails and efficiency.

As ever, you get what you pay for.

 

[flay]

thanks for the quick reply!

I had a look at the review of a psu on this very forum a sec ago, and his rather nice rig with a 4870x2 on full benchmarking load only drew 550ish Watts.

Thus I'm thinking that as long as I check the Ampage on the rails of the 750W psu's I listed I should be ok? especially as they are certified xfire/sli compatible?

 

[flay]

I've been having a bit more of alook around and I think I might go for this:

http://www.overclockers.co.uk/showproduct.php?prodid=CA-017-TG&groupid=701&catid=123&subcat=1100

one final question though. a 4870 uses two 6pin connectors. this psu comes with 2x 6pin and 2x 6+2pin. so if i want to xfire another 4870 later, could I just use the two 6+2pin connectors as 6pin connectors by not attaching the '+2' bit?
Or do I actually need to find a psu with 4x 6pin connectors?

thanks for all the help guys.

 

[flay]

this tagan psu is listed on the amd website:
http://game.amd.com/us-en/crossfirex_components.aspx?p=3#ATI%20Radeon%E2%84%A2%20HD%204870

so does that mean I should be absolutely fine with it powering 4870 crossfire?