In contrast to your experience, I have had the most pleasant experience with the Creative Sound Blaster X-FI HD. I purchased it to resolve a need for a versatile interface between PC and Home Theater. With this device I can digitize LP's, send S/PDIF optical to USB, and convert USB to S/PDIF optical, or analog. Right now, I'm using the device to play iTunes through my Sony TA-E9000ES pre/pro DVD optical S/PDIF input, which accepts a 24/96 signal. Using the device in the manner described, there is no noise. In fact, what's so impressive is that with this relatively inexpensive interface I cannot distinguish iTunes material stored at 256 from SACD or vinyl of the same music when played through my high end home audio system. Others who have systems like mine have shared with me that they have had the same sort of experience with the X-FI HD. Even at very high volume there is no low level noise when I use my laptop with battery power. My high end system simply has not sounded better with iTunes, using the X-Fi as an interface. And, since I cannot distinguish now between iTunes, SACD, and vinyl, I see no need to consider upgrading. The only thing I might do is upgrade my plastic optical Toslink cables to ones made from glass.
BTW, is it possible that your X-FI is not set-up correctly, or interconnects are not fully inserted? Either could produce noise such as you have described. Also, the noise may be originating with another source which, through the X-F's silence, is coming to light.
Edited by sterling1 - 5/2/11 at 5:03am