|The 8400GS is a low end card with low power requirements, maybe 40W max under full load, say 3A from the +12v. Each HDD pulls about 1-2A from the +12v.|
Is there some reason you prefer the Storm II with its dual +12v design over a unit with a single +12v rail? Did you check the specs for the Corsair posted by grasshopper? 600W, ATX12V v2.3, 80 Plus certified, active PFC, single +12v @ 40A, 5 yr warranty, only $50 after rebate.
Rosewill has some decent units as well, but the warranty isn't as good.