I've bought something quite similar last week from Tigerdirect.
XFX nForce 680i LT SLI Socket 775 Barebone Kit - Intel Pentium D 925 3.0GHz OEM, 2 x 512MB Video Cards, 2GB DDR2 PC6400, ATX Mid-Tower Case, Clear Side, 500 Watt Power Supply.
It seems that the powersupply (Ultra 500W ATX) is not right for this system. Once all hooked up, there's no power. Beside the 20 pins connector, the powersupply got a 4-pin ATX 12V connector instead of a 8 pin ATX, which is strongly not recommanded according to the XFX motherboard manuel.
Call up Tiger this morning - They know about this, as there are three more customers with the same problem. They will call me back today (3th Dec)and hopefully exchange the powersupply asap once they figured this problem out.
According to Tiger, it is a 'marketing' problem. I've to point out that I never had a problem with them before.
Marc