I have no experience with external audio equipment, so I can't advise there, but one thing I would recommend is checking the volume controls for each device. I've found that muting unused devices has helped. I don't use spdif, cd audio, midi or line in, so I mute those and any background noise they were creating is removed. However, that doesn't alleviate the problem entirely, as my onboard sound just isn't up to scratch either. I get the lovely electronic chitter chatter noise in the background when it's perfectly quiet. The only way I can get rid of that is muting the sound altogether. Not the best option but works every time. []