Huh? That PSU ought to have two 6-pin cables, and that's what you should be plugging straight into the video card. Don't use the molex connections for that. You only use molex-to-6-pin adapters for when you don't have enough direct 6-pin cables.
I'm guessing that's what happened -- you saw the adapters included with the card and figured you were supposed to use them. But do it the way I said and use the now-free molex connectors for the fans.
Unless you are talking about something completely different, in which case, it would help to know more. I don't think it's possible to crossfire 5870s on a 600W power supply, which is why I ignored that option.