Some (though not all) SATA drives have both old & new style power connectors. For instance, I just bought & installed a Maxtor SATA drive, and it had both types of power connectors built in (along with a stern warning to use one or the other, but not both).
If you buy a drive that has only the new-style power connector, you can get an old-style-to-SATA-style power adapter for about $10. Odds are, anywhere you might buy your SATA PCI card will also carry the power adapters.
OS X 10.8.2
MacPro 4-core 2.9Ghz
Apple 23" Cinema Display