Grpahic Card power supply.

I have 1000W xps 710 power supply which deliver power to Ati 4870 x2 through one 6 pin and one 8 pin .
The 8 pin is made from 2 x 4 pin v12 molex that came with graphic card. But I will need one 4 pin connectors. What is the safest way to split this ?? use 4 pin Y spliter or use dual 6-pin PCI Express to single 8-pin PCI Express or 20 pin to two 4 pin connectors?? As well I have the same 8 pin connector for my motherboard which is made from one 4 pin link >( http://www.plinkusa.net/products/Cable-AD4-8Pin.jpg ) but I don't think that would be safe to use with ati 4870 x2 ??

Thanks

4 pin
\/
4 pin - 4 pin
\/ \/
8 pin
\/
Ati 4870 x2

or

6 pin 6 pin
\/ \/
8 pin
\/
Ati 5870 x2