I have an Audigy with a Promise Ultra 100 (8 IDE devices total) and have not heard the pops and clicks. I do have a few recommendations:
1. Make sure the soundblaster has its OWN irq. You can have it share the Firewire irq, but NOT the basic windows sound IRQ.
Creative labs recommends the audigy has 3 of its own irq's, impossible. Check your motherboard manufacturer and make sure that it is not in a slot that is hardwired to share an irq with an onboard device. (Ex. ABIT BH6, APG shares with PCI slot 1, and Onboard USB shares with Slot 4 AND Slot 5.)