I'm wondering if I have a PSU strong enough to handle another 8800gt in SLI.
I saw the new System Builder Marathon sub $1000 PC used a 400W PSU, so will my 680W PSU work? ( they used this one http://www.newegg.com/Product/Prod [...] 817256032) It seems to have more AMPs, but will it work?
My current system:

-Apevia APEVIA X-TELSTAR-JR G-Type X Steel ATX Midtower Case
http://www.newegg.com/Product/Prod [...] 6811144211

--APEVIA ICEBERG ATX-IB680W-BL 680W ATX12V / EPS12V PSU
http://www.newegg.com/Product/Prod [...] 6817148028

--AMD Athlon X2 5000+
http://www.newegg.com/Product/Prod [...] 6819103211

--4GB DDR2 http://en.wikipedia.org/wiki/DDR2_SDRAM 800Mhz OCZ TitaniumRam (Timings are 4-4-4-15)
http://www.newegg.com/Product/Prod [...] 6820227270

--Asus M2N-SLI Deluxe Motherboard (nForce 570 Chipset)
http://www.newegg.com/Product/Prod [...] 6813131013

--Nvidia GeForce 8800 GT 512MB Video Card
http://www.newegg.com/Product/Prod [...] 6814143118

--Western Digital 320GB Hard Disc Drive
http://www.newegg.com/Product/Prod [...] 6822136098

Yes, your crappy PSU will power the second card fine. In fact, if my math is correct, that 680w unit is rated at 880 watt according to the label.

All sarcasm aside, you overpaid for a cheap PSU whose rated power is way more than you needed. A quality 400 to 500 watt PSU with active PFC will cost slightly less and pay dividend from day one by being more efficient and cooler not to mention being more reliable and less likely to burn out your hardware.

EDIT: bring -> being

That's not entirely true; PSUs are usually most efficient when only using about 80% of their max power. Besides, getting something that's more than what you need isn't so bad; it leaves room for expandability. For example, if he ever decides to get a nicer motherboard, quad core processor, and, say for example, two 4850s.

Go ahead and use the 400w that Soderstrom recommends, even though it only puts out 360w when it gets hot and has a 1 year warranty which is about the worst in the industry. Even though it'll be over 90% of capacity at load....if it can even handle the load. It's a brilliant choice for a freaking power supply in a SLI system.

You'd be much better off with this: Corsair TX650

I've recommended the TX650 like five times today and I don't regret it at all. Corsair PSUs are unbelievably good for the price.