Power supplys, wattage, voltage, ampage, single rail vs double rail?

Question

im in the market for an inexpensive atx power supply between 400 and 500 watts

Whats the better budget power supply for my rig?

my machine:

amd athlon 64 x2 2.6

asus motherboard

3gb ram

gforce 8600gt

power supply:

epower 450xp

29.99 (promotional price)

450watts

12volts @ 28amps

(one thing i never heard of this brand and another there are only 2 reviews compared to 40+ on others but bother are 5 stars, those could be biased manufacturers reviews though)

raptor r500

$44.99

500w

12v1 @ 18a

12v2 @ 18a

rosewill 500

$49.99

500w

12v1 @ 18a

12v2 @ 16a

rosewill 550

$64.99 (free shipping)

550w

12v1 @ 20a

12v2 @ 18a

sli ready

nice mesh cable covers

cooler master extreme power plus

$39.99

460w

12v1 @ 18a

12v2 @ 18a

cooler master extreme power plus

$49.99

500w

12v1 @ 18a

12v2 @ 18a

coolmax

$49.99 (free shipping)

450w

12v1 @

12v2 @

they all run cool and quiet according to the manufacture and reviews

my question is do i need 2 12v rails?

also if i have a 450w with 2 12v@20a or 500w with 2 12v@18, which one does more work?

im vaguley familiar with power supplys so any extra information that helps would be much appreciated.

Answer 1

Rosewill is a great company. Any PS 500 watts+ will work great with your machine.  

Answer 2

This Coolermaster 460w is only 39.99 after rebate.

http://www.newegg.com/Product/Product.as...

Answer 3

I had a coolermaster fail on me, right out of the box, bad capacitor.  So I advise a Roswell, I understand on good authority, they are good power supplies.  There are pros and cons on single and double rail, and I don't see the difference myself...as if in a double rail, one rail goes out, the PSU needs replacement and if a single rail, the same.

As far as work is concerned, it all depends directly on the efficiency of the PSU doesn't it?  So component integrity is paramount and if you are getting a cheap power supply then you can bet you are getting a low efficiency rating and that translates into low work output.