Convert 8-pin pci-e connector to a 6+2-pin?

I'm looking at the GTX285 video cards but they need a total of 42A. My PSU is a Cooler master 850 watt pro. My four 6-pin 12v rails are rated at 18A and my two 8-pin 12v rails are rated at 28A. The problem is that the card needs at least 42A and it has two 6 pin connectors and my 6 pin connectors are only rated at 18A so 18A+18A=36A, so I'm short. My 8 pin connectors are rated at 28A so if I use one of them (28A) plus a 6 pin (18A) I could get 46A which is more than enough to power the card. So my question is this..can I convert the 8 pin into a 6+2 pin so that I can plug it into the 6 pin slot on the card? Thanks for any help that you can give.

the card does not need 42A the entire system does I think....

If it could not get by on 2x6pin pcie connectors they would have put an 8 pin socket on the card.

Yes, that is for the system. Those cards dont take more than 150-200W or so on their own. Even with pair of them, that PSU will be just fine. Dont make it harder than it is. Just plug it in and go.

Cool...Thanks for the prompt replies. I guess that I don't need to worry about it afterall.