I'm trying to do a cheap upgrade on an old fairly cheap system, but despite everything I've read don't really understand dual +12V rails. I've got a dell dimension 4600 with a 2.8GHz pentium 4. I'm going to upgrade the ram to 2gb and was looking at buying an ati radeon hd3650 agp graphics card. A 550Watt or greater power supply with 30Amps on 12 volt with 2x4 power connector is recommanded. I'm hoping to get a psu < $60 and was looking at this, but wasn't sure whether or not 2 12 volt rails at 20A was ok instead of one at 30A.

Any help/suggestions would be greatly appreciated.

Yep that's a cheap PSU, it should kill your system quite nicely.
Look up the tier 1 and 2 PSU's here on toms.
Then get one of them. I buy PCPower, and have had good results with them.

I'm surprised a HD3650 AGP card has that high of a power requirement. Other HD3650 cards i've looked at require 300w to 400w. Could you link where you're going to buy it at ? I honestly wouldn't recommend a Sunbeam power supply to anyone. The graphic card will pull power off both rails, so 2 at 20amps would be fine. This power supply at $45 after rebate would be a much better choice. OCZ StealthStream 600w
http://www.newegg.com/Product/Prod [...] 6817341010
If the cost of that 3650 is over $130 you'd be better off getting the HD3850 AGP
http://www.newegg.com/Product/Prod [...] 6814102730

If your going the cheap route (which I don't recommend), at least get your 30amps:

http://www.newegg.com/Product/Prod [...] 6817371006

The Earthwatts is great. Amazing price after the rebate.

After taking bobbknight's advice and looking at the tier 2 psu's I was thinking about the ocz GameXStream(just in my price range), but saw the one your suggesting which seems extremely similar and $15 less and now with your suggestion I'm thinking that it may be my best choice(After some forum searches as well).

Also the hd3650 is $83 on newegg, and I just don't think it will be worth the $50 i don't really have to get the 3850. I need to buy textbooks.

thanks for the advice. clearly i'm clueless when it comes to power supplies.

Thanks Kite, the one at newegg ....the HD3650 AGP with DDR2 is not the same one that is in the link from Sapphire that you showed. That one has DDR3 RAM and the AGP interface. I was confused.
http://www.newegg.com/Product/Prod [...] 6814102762

You're right. I actually got the link to the sapphire page from the newegg page you posted and didn't really check to make sure it took me to the right page. I just scrolled down to the system requirements because I was sure i was gonna need a new power system.

The hd3850 is definitely tempting but I'm positive the hd3650 will be fine for its intended use.

Get somthing decent from Rosewell (spelling)

rosewill doesn't make good power supplies, they're all junk.