As I browse thru Creative Cow, I am sitting here building two brand new Apple Nahelem MAC Pro Quad Core computers with two brand new Kona LHi cards. I have just finished the first unit. Slot 2 is empty. Slot 3 is the storage card. Slot 4 is the Kona LHi. You can interchange slot 3 and 4.
If I had a hi speed storage card (like an ATTO R380, Cal Digit RAID card, or Areca 1680x) I would put this card in slot 2 - a card that would benefit from the extra lanes.