Yes one 6 pin PCI connector is required.
Wattage specs are individual per power supply, ie. I have a Antec 500W Smartpower 2.0. Which has dual 12V output rail, which has a max rating of 480W combined rails.
http://www.antec.com/us/productDetails.php?ProdID=26500
For those with a modular supply with multiple rails, one would have to check the wattage per rail, and may have to combine rails if the wattages do not meet spec.
You have read what needs 30 amps? The 4850?, I highly doubt that. Let me know where you read that.
6 pin PCI express power leads are standard and come with most all new PSU's. As well as card manufacturers usually bundle 2xmolex--> 6 PCIex for those without proper connectors.