That many drives shouldn't be a problem. Staggered spin-up will guarantee that you'll be fine, although a 460-500W supply will likely handle it anyway.
However, if you are still worried, it's very easy to rig up a second power supply to handle some of the load. Just place a relay to bridge two wires upon receiving voltage on the main supply, and the second supply will switch on/off in conjunction with the main one. I believe the Cooler Master Stacker case actually has built-in room for two PSUs.
Like I said, though, you should be fine with a half-decent PSU of reasonable wattage-rating. Not Antec... but Fortron, Enermax, Seasonic, PCP&C, as long as they are at least say 450W, should all do fine.