Use the 6pin (since you have one) and an adapter for the second 6pin. My cards both came with adapters (although I didn't need to use them), but if yours doesn't, you can pick one up. I think you'll need 2x 4pin molex connectors for 1x 6pin adapter.
Like phishy said, as long as you have enough 12v amps, it really shouldn't matter.
edit: Looking at your link, the card comes with 2 adapters.