You can use a molex to 6-pin adaptor depending if your PSU is up to the task.
What is your current psu make and model?
Sorry, not sure of the make right now, so I'll let you now once I've opened up my comp.
Almost any good quality PSU that is of adequate wattage/current for you card will have the necessary connectors.
Get an idea of the wattage necessary here: http://www.thermaltake.outervision.com/
And check out the PSU's here: http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007657%20600014024&IsNodeId=1&name=801W%20-%20900W
(I linked to 800W-900W PSU's because I figure that's what you'll be looking for.)
Well, at the moment I've got a 400W supply, so I'm gonna have to upgrade. Now that I know the ballpark wattage I need, I'll be able to find it more easily.