Every motherboard is a bit different in how their PCI slots utilize IRQ's, and also as far as which slots are bus-mastering capable. Most motherboard manuals are now including diagrams to show such usage.
Here's just one example for a motherboard in one of my machines:
PCI Slot 1 shares an IRQ with the AGP slot
PCI Slot 2 has an IRQ of its own
PCI Slot 3 " " " " " "
PCI Slots 4 & 5 share an IRQ with USB
So, find out the IRQ usage for your particular motherboard, and then install your PCI cards accordingly. I'd put the soundcard in a slot that has its own IRQ, it sounds like the FAQ you refer to is saying that Slot 2 & 3 share an IRQ on your board.