How are you planning to hook up the storage? Many operations like this use Fibre Channel (multiple computers can connect to multiple large storage devices at high speed). I am unaware of any way to get an iMac to talk to Fibre Channel storage, and can't even see what would be possible, since the iMac lacks any kind of expansion slot. Your only real options are FireWire 800 (storage on each computer) or Gigabit Ethernet for NAS, and both top out below 100 MB/s. Can you wait for the Mac Pro refresh? - there's a persistent rumor about a lower-end Mac Pro that will be priced more competitively with the iMac, yet offer viable disk options - even if you don't go with Fibre Channel, a Mac Pro offers you four (arguably six - some people toss hard drives in the optical bays) fast internal storage connections plus slots to add any interface you want (eSATA, SAS,Fibre Channel or whatever) - as opposed to ONE fast connection, which has to be the boot drive, on an iMac. Right now, the Mac Pros aren't price competitive, but that may change.