Yes that was a simple temporary solution made up by CM, which I personally wont believe. So as Blackbird said get a decent HASWELL compatible PSU for your own good. BTW the sleep states are automatically disabled in most Mb's though. But still get a decent PSU like this one :
A single GTX 780 will require 42 Ampere on +12V rail of a 550/600W PSU, the card only require 250-270W (reference and non-reference) of power, so in SLI the cards will need approx. 540W, so 750/800W PSU will do. But if you get a bigger PSU it will be better for you, it wont cost you a penny more to operate.