Quad SLI is when 2 cards are used each containing 2 GPU (9800 GX2, GTX 295).  Quad SLI with a dedicated PhysX card with every PCIe slot at x16 can be accomplished on the SR-2 motherboard.

In order for all 3 cards to be running at x16, the cards can only be used on slots 1, 3, 5, or 7.

If slot 2 is used, slot 1 will become 8x

If slot 4 is used, slot 3 will become 8x

If slot 6 is used, slot 5 will become 8x