utter utter rubbish, tell him so and buy your hdd from elsewhere he is just trying to sell you a new PSU. I'm running 2 x 2TB, 2x 1TB + 1x 1.5TB off a 365W supply and i'm only pulling 65W from the wall.
However give us your full system specs as it is very easy to use more than what a 450 can cope with.