I run Vista 64, 4GB of RAM and X-Fi.
I used to have the static issue; it's annoying as heck. A workaround is to disable the X-Fi in device manager, and then re-enable it, eliminating the static (albeit temporarily).
However, about 3 weeks ago a hotfix popped in WU that, while not specifically about the X-Fi, mentioned sound problems in Vista 64. After installing it the issue hasn't cropped up again. Might be a coincidence, perhaps one of the patched in the reliability and compatibility packs released a few weeks back fixed it.
Or perhaps it's just waiting around the corner to happen once again.