My X-Fi XM has been on three separate motherboards (Intel 925X, ASUS P5W DH and my current) with never having the popping or crackling issue, though the newer drivers have been able to address those who did, it's worthwhile to check. It didn't play so well with nVidia chipsets, IIRC.
What I did have was more of a buzzing noise through my headphones, usually when I was using USB flash drives. Turns out it because of interference through the front panel. Moved my headphones to my speaker jack, it's been clear ever since.