thanks for your reply.......... any suggestions for a card that will run diablo 3 w/ 300watt card
Not many video cards will run with that little power. OEMs like Dell intentionally put the smallest possible power supplies in the computer to prevent you from upgrading. That way they make more money off you for upgrades.
I'd recommend just getting a new power supply, at least 500W. Do not
get the cheapest unit you can find. Cheap PSUs will kill your other components. If you don't spend at least $40 on the unit, you're going too cheap.